Search Results for: machine doubling

Machine Doubling (MD)

(All of the information is also at ErrorVariety.com)
Machine Doubling (Damage) (MD or MDD):

Below is a close-up illustration of Machine Doubling (MD) found on the reverse of a 1983P Lincoln cent (top) and then a close-up of doubling found on the Doubled Die Reverse listed as DDR-001 (1-R-IV) (bottom). Notice the flattened out manifestation of the MD; the irregular appearance; and change in physical characteristics of the doubled area. Compare to the rounded and raised true doubling of the Doubled Die (bottom).

Machine Doubling has been designated with two types: Push Type and Slide Type (showcased in a new post down below). MD Push Doubling is extremely common and has hypothetically been suggested as a product of a loose hammer or anvil die, after the strike with some of the original energy of the strike transferred, there is a rebound and a shift that sends the die back down, typically in a slightly altered position where it subsequently hits the design on the coin and pushes it down. The result is a flat, shelf like area of the design that appears to differing degrees as being doubled.

This is a reductive process that is opposite of Die Variety Doubling and some forms of Error Doubling in that part of the design is altered or lost whereas Variety Doubling the doubling adds to the size of the device in question.

MD can impact as little as one letter or whole parts of the coin. It can be random or mimic classes of Doubled Dies in appearance. If the mintmark is doubled similarly to the date, odds are very high it is MD. One must remember mintmarks were added to the die AFTER they were impressed with a HUB. What that means is the die is doubled BEFORE the mintmark was punched into the die. This is true for all denominations of coins until 1989 as the Mint stopped punching mintmarks in 1990.

The illustration below shows a 1989 Lincoln that has MD on the date, the ear, the Y in LIBERTY and part of the coat. You can see the push down was only partial and at first glance almost looks like doubling. The area in blue (MD2) on the date represents the compressed area and along with the preceding graphic (MD3) shows how the doubled areas, if removed, cut down the size of the device and make it irregular. The illustration of 1989P 1DO-005, a Class VI Doubled Die with extra thickness in the date, and 1972P DDO-00, a very strong Class I, offers a contrast to the MD in that the doubling adds to the normal size of existing devices and remains rounded.

(MD4) is a close up of the flattened area of the 8 that also shows metal flow lines from the MD impact. At the bottom, 1909P DDO-001 shows class IV doubling RTY in the form of separated images. While not as rounded as some examples, the serifs technically are notched and there is no loss in size of the primary device as in the example (MD5) with MD on the Y (to the left).


Terminology:

Machine Doubling is sometimes called by a seller or a buyer as: strike doubling, machine doubling damage, sheer type doubling, mechanical doubling, ejection doubling, field doubling, shelf doubling, double date, and erroneously as a Double Strike or a Doubled Die.

EBay:

there is currently no place where doubling and its many forms are more confused, through ignorance and deception than eBay. The abundance of readily available information that accurately explains Varieties and Errors is seemingly outmatched by the ignorant, misguided buyers and equally ignorant or dishonest sellers who peddle garbage. The auction titles and descriptions often contain inaccuracies or made up terms such as: double dies, double dyes, double dates, double die date, DDO strike variety, mechanical DDO type, doubled date obverse, etc. Most often sellers are only able to describe what they see as “doubling” and generally know very little if anything about types of doubling or classes of Doubled Dies. Another range of auctions try and take the ’55 poorman’s double die (PMDD), a misnomer, and further apply that term to coins with MD on the ‘69S or ‘72P. In other instances the seller offers a coin as a possible Doubled Die or double die with a question mark (??) at the end of the auction title. In cases like this the sellers will offer vague descriptions, sometimes poor photos of coins with MD or DDD and make the promise of the buyer either getting potential high value coin for very little or some sort of glory as the discoverer if, you the buyer, submit the coin for authentication later. All hogwash designed to deceive buyers into buying a worthless coin.

Below are more views of MD. Here we have three different 1983 Lincolns that all exhibit varying degrees of MD and all could easily be sold on eBay as DDRs. They are contrasted by two 1983 DDRs: DDR-001 and DDR-002. The Double Dies are rounded with distinct secondary images while all the examples of MD show compressed metal and the reduction in size of the effected device. The memorial, the O in ONE and parts of UNITED are very frequently doubled by MD on any and every year of Lincoln cent. DDRs very rarely show doubling on the memorial itself, and it is always rounded.

There is nothing as classic as the classic Machine Doubling found on 1969S Lincoln cents. Many collectors have thought they hit the coin-lotto by finding a very common machine doubled BU cent while roll searching. The key typically is that the mintmark ‘S’ also has MD.
Below the ’69S is a another classic example of flattened, shelf-like MD on a 1941S Lincoln.

This final set of illustrations shows typical MD found on the reverse of many Lincoln cents. Flattened areas with no notches and a reduction in the size of the devices. Compare the “of” with MD to that found on 2004P DDR-001 or 1964P DDR-001 which has notches, clear separation lines, rounded doubling and extra thickness.

Below that is a case of isolated MD on Lincoln’s chin, compared to doubling found on 1971S DDO-002. Doubled Dies with doubling of Lincoln’s profile are very rare while profile doubling from MD is rather common.

__________________

Jason Cuvelier

The Non-Hub-Doubling Resource Page

I decided to collect here, in one place for your reference, all of the different forms of doubling that you may come across while searching Lincolns.  There are many pitfalls on the path to recognizing the classes of doubled dies, so I endeavor here to show a comprehensive list, with illustrations, of all of the forms of doubling which are not the result of hub doubling. Again, what follows are not doubled dies, though are often confused as such.

Section 1: The basics – the following are the most common causes of doubling and do not generally carry any premium.

Machine Doubling (Also Machine Damage Doubling, or Strike Doubling): This occurs when a loose die bounces (push-type machine doubling) after the initial strike and hits the planchet again in a slightly offset position, flattening a portion of an already struck device, creating a “shelf-like” doubling effect that cuts into the normal size of the device. This is often misconstrued as a doubled die by novices, but is common and essentially worthless. Sometimes the die will “slide” rather than bounce, creating a smeared look to the devices. (slide-type machine doubling). Ejection doubling is another form of machine doubling where the coin “sticks” to the anvil die when being ejected from the striking chamber. In addition to the examples below, please see Jason Cuvelier’s excellent tutorial Here.
1955pluralpluribusslidemachine doubling

 

 

Die Deterioration Doubling: A circumstance that occurs from die deterioration whereby the devices show a duplicate image on a coin. As metal must flow into the recessed areas of the die during the strike to form the devices on a coin, the edges and corners of the design elements on the die begin to wear. Eventually, this wear shows as a doubled image on the coins they strike. On Lincoln cents, the date and mint mark are often the first to show this doubling, since these devices are in the middle of a field with no other counter-relief to aid metal flow. Die deterioration doubling usually exhibits on the rim side of the devices, as in the example below. The 1955 “Poor Man’s Doubled Die” is NOT a doubled die at all, rather it is an example of die deterioration doubling. Dies in this time period were grossly “overused” resulting in many coins showing this common form of doubling. Die deterioration doubling is not generally considered collectible. Please see Jason Cuvelier’s excellent tutorial on the subject Here.
die deterioration doubling2 die deterioration doubling1

 

 

Split Plate Doubling (Split Line Doubling): This occurs only on copper-plated zinc cents struck from mid 1982 to the present. During the striking of plated cents, the plating is stretched in order to form the raised design elements. Whenever relief is created from a flat surface, there must be expansion of the overall surface area, thereby putting stress on the plating. Sometimes, the plating will split on the rim-side of the devices, exposing the zinc core. The exposure will be in the same shape as the design elements, thereby creating a “doubling” effect. The exposed zinc is blue-ish in color. In addition to the examples shown below, please also see Jason Cuvelier’s thread on the subject Here:
splitplatedoubling1 splitplating

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Section 2: Master Hub.  These are all common and hold no premium.

Reduction Lathe Doubling: This form of doubling occurred on several master hubs in the Lincoln cent series. Since master hubs were often re-used over a span of years, this type of doubling will show on EVERY cent struck over a period of years that the master hub was used, and therefore carries no premium. Some refer to this as “series doubling.” The Janvier reduction lathe was the machine that was used to transfer the image from the galvano to the master hub. There were 2 arms, one which traced out the image on the galvano, while the other cut a smaller version of the design onto the master hub. This would require many passes by the arm to do, and if there was a slight slip of the arm during the process, the design would be recreated in a slightly different place, creating this doubling. Some of the master hubs that had reduction lathe doubling on them were:
1. The 1909 reverse master hub, showing on the bottom of some of the letters in CENT and UNITED STATES OF AMERICA. This showed up for several subsequent years as well.  Images by Jallengomez.
1909 Reduction Lathe A 1909 Reduction Lathe B

 

2. The 1909 obverse master hub on the BE of LIBERTY and the W of We. The extra thin bar on the vertical of the B and the extra notches on the W can be seen spanning many master hubs and exhibits for many years until they were redesigned in 1955.


RLDonB

 

3. The 1933 obverse master hub and its successors used in 1935, and from 1937 until 1955, which showed a bold doubled forehead and front hair curl.
redlathefore1redlathefore2

4. The D of God had “doubled” vertical bar starting with the 1922 Master Hub and continuing until the mid 50s.

Additionally, there are many master hub anomalies confined to individual master hubs. For example, from 1937 through 1942 (excepting 1938) the R in LIBERTY had a notch on the top left corner. This exhibits on all dies spawned from this master hub and is NOT the result of a chipped working hub.

 

 

Section3: Master Die. Again, these are common and hold no premium.

There were many engraving issues on master dies, which are often confused as hub doubling. (Reused master hubs had to have the last digit or two engraved into the master die.)

1. This engraving doubling is often misconstrued as a doubled die on 1960 small date cents.

2. All 1965 cents show this notch on the 5.

3. All 1973 cents show this notch on the 3.

4. 1941 cents on the 4

5. 1944 cents on the 44

6. 1940 cents on the 40

7. 1932 cents on the 32.  Photo courtesy of grnwavdav (David Miller)
32

An additional example is this doubled forehead, nose, and chin seen on 1946 cents.

There were many other cases of master die doubling, too numerous to demonstrate here, but the most often confused case is in 1972.  There were 2 master dies used this year, one showed “doubling” and one did not. Jason Cuvelier’s tutorial on this subject can be seen here.

 

Section 4: Working hub. Again, these are common and hold no premium.

Channeling (Trenching): On many Lincoln cents from the 1920s to the 1950s, we see an incuse “channel” surrounding parts or all of Lincoln’s bust. It is believed that many working hubs had this channel engraved around the bust, possibly in an effort to prolong the life of the working hub, or to sharpen the profile, although we are not certain of the reason. Once believed to be a master die issue, it is now more commonly believed to have been done on individual working hubs, as it shows inconsistently on coins within a given year.
MDO1943trench_zps13df464f

 

 

 

 

 

 

 

 

 

 

Section 5:  Doubling on errors. Unlike the other listed forms of doubling, these errors can carry  strong premium.

Grease Mold Doubling (Stiff Die Fill Raised Design Element Doubling): error-ref.com‘s term for a recently discovered form of doubling being found on cents from the mid to late 1990s, affecting the terminal digit of the date. In this term, the word “mold” is used as in “jello mold,” not as in “black mold,” or fungus. Presumably, a greasy/gunky film covering the die surface can become hard enough from the striking process that it forms a solid mold of the design element. If this solid mold of gunk begins to shift into the field from its original position, and since it is in the same shape as that portion of the die, it can create a raised design element in an offset position. Of course, since this mold will be somewhat smashed during the strike, the slightly raised element will be larger that the original design element. In addition to the link at the beginning of the entry, please also see this article by Mike Diamond for more information. The images below were donated by jallengomez and Joel.
Greasemolddoubling2 Greasemolddoubling1

 

Double Strike: A coin that failed to completely eject from the striking chamber and was therefore either partially or completely struck a second time. This should not be confused with Strike Doubling, which is another term for machine doubling.
1918_Doubled_Struck_Cent

 

Section 6: Doubling on the Mint Mark.

Broken Mint Mark Punch: Sometimes the punch that is used to make the mint mark on a working die can be damaged or broken. Each coin struck by these dies will also show these irregular mint marks. They can sometimes resemble a re-punched mint mark as is the case on this 1979D cent. This broken punch was used on many 1979D working dies.

79Dbrokenpunch

Section 7: Doubling from post-strike damage

Rippled Coin: This is a form of post-strike damage that causes a doubling (or multiple) effect on the devices. Just as the name suggests, the coin exhibits ripples on its surface, often following the contours of the devices giving them a doubled/tripled/quadrupled appearance. The exact cause(s) are unknown, but contact with an acidic substance is one theory. Photos courtesy of forum member Liz.
rippled-6rippled-7rippled-5

Die Deterioration Doubling (DDD)

I have been working on a quick visual analysis of Other Forms of Doubling (OFD). (This whole page plus other examples have been archived here: LINK.)

Here I have illustrated Die Deterioration Doubling (DDD) on both new and older Lincolns. Illustration a. is a 1989D with DDD that is often mistaken for MD (what I had thought for a time as well) OR for beginners, confused as a Doubled Die. You can see in the first picture that the date has a ghostly doubled companion, by changing the light (photo 2), one can see the typical orange peel associated with DDD on older Lincolns is present here as well. (Also note the mintmark has Split Plating Doubling.) Below for comparison is a 1989P with clear Machine Doubling( (MD) and finally a 1989P 1DO-005 with class VI extra thickness in the date.

Illustration b. shows a common LDS examples of a 1955 with DDD on the second 5 and across IGWT (sometimes called a poorman’s double die, a misnomer) in LIB of LIBERTY and the 4 of a 1954. At the bottom is a 1955 DDO-002 with separation and notching for comparison with a real doubled die.

a.

DDD_a

b.

DDD_e

Jason
__________________

Jason Cuvelier

Plating Split-Doubling (Split-Line Doubling)

Plating Split-Doubling (AKA Split-Line Doubling):

At this point there is no official phrase for this phenomenon; web searches lead Plating Split-Doubling to Ken Potter and Split-Line Doubling to Mike Diamond, but it is unclear who coined either term. The characteristics are: a split in the copper, revealing a light blue to greenish area (which is exposed zinc), that shadows a device and makes it appear doubled.

Plating Split-Doubling is notoriously misidentified as RPMs, Doubled Dies and on Broadstrikes as having been Double Struck (when it has not).

The phenomenon is commonly located on either the obverse or reverse of copper plated Lincoln cents. Plating Split-Doubling is also boldly found on some Broadstrikes and Off-centered Lincoln cents. While it can be found almost anywhere, it specifically tends to inhabit the regions nearest the rim and is associated with the design elements. The devices most frequently identified on a normal strike are the mintmark (MM), USoA, INGWT and sometimes parts of the memorial. The split itself can be very thin and hug a device or some distance from a device and wide to the point that it appears almost comical on some Broadstruck Lincolns.

While it would seem possible that the split is a tear that is facilitated by the raised struck parts of the coin holding the copper in place as it travels too quickly and too far – it appears more likely the sharp edge of the incuse die devices weaken and help to instigate the copper to split open and reveal the zinc as the copper it is stretched too thin. Why it happens inconsistently appears unknown.

Below are two examples: the obverse of a 1993 Off-center Lincoln and the reverse of a dateless Broadstruck Lincoln, both exhibit Plating Split-Doubling. The Off-center has the appearance of an extra profile while the Broadstruck has various parts of the memorial splitting open. Points 1, 2 & 3 (on the illustration below) appear to originate from the same location at the first moment of impact next to the portrait of Lincoln, and then they appear to travel apart as the copper is over stretched.

Below is a 1992D and a 1989D both with commonly seen Plating Split-Doubling on the MM and the devices on the reverse, notably USoA and the memorial. The black arrows in the first photo show the splits while the white arrows show mild Machine Doubling that has also occurred.

Here is the approximate distance for specific devices from the rim on Lincoln cents:<
LIBERTY: .5mm
IGWT: .3
MM: 1-1.5mm
Bottom of bust: .6mm (not sharp)
USoA: .2mm
ONE CENT: .2-.4mm

Most splits are occur on LIB, the upper parts of IGWT, USoA, the lower parts of ONE CENT, the date, the outer parts of the memorial and, while not as close to the edge yet yielding many examples, the lower and inner loops of the D MM.

__________________

Jason Cuvelier

Class IV (Offset Hub Doubling)

Class IV (Offset Hub Doubling)

This class of Doubled Die is produced when two hubbings have their centers misaligned. It is characterized as having doubling that is evenly spread in one direction unlike Classes I & V where the misalignment-event shows rotation at or near the center (I) or at or near the rim (V). Doubling is often rounded, found closer to the center and when identified on numeric or alphabetic characters, shows notching.

It has been hypothesized that the reason many examples do not show doubling near the rim is because the first hubbing only received a partial hubbing. Such an incomplete hubbing would result in design elements not being pressed deep enough in the middle of the die, and not at all along the perimeters; remember the die originates in a conical shape until it is completely pressed down so the outer devices may not have been hubbed the first time around. A few examples that show doubling primarily in the center portions are 1909P DDO-001; 1941P DDO-005 (1DO-006); 1942P DDO-002 (1DO-005); and 1942S DDO-001

Below is a facsimile of a fictitious 1960P with a strongly doubled Class IV DDO. In this case the first hubbing would have been centered and complete with the second hubbing having its center oriented N-NE from the first. It should be noted that this example is showing universal doubling on all design elements (including the whole portrait) which has never been documented.

Below is 1983P DDR-001, which exhibits a large spread going North, it is stronger than the above hypothetical, but the central elements only show doubling around the parameter of the memorial and in a few sections of the building itself (like the upper portions of the columns). Notice the notching (a clear indication of hub doubling), rounded secondary images and how the secondary hubbing shifts consistently in one direction.

Next we will find two overlays demonstrating that the ’83 DDR has simply a wide north shift in the hubbings. In the second picture green is first hubbing followed by red second (the first hubbing appears as if it were on the first).


Another bold example, yet displaying only a partial first hubbing is 1984P DDO-001, with its widely doubled ear, beard details, back of head and bow tie. This DDO also appears to be ever so slightly rotated as the second piece of the bowtie resides further away proportionally than the second ear. If correct, the center of rotation would be off at least a centimeter to the side of the die past IN of IGWT.

 

Notches: As has been pointed out by most variety specialists and attributers: notching, even though the doubled areas are shallow, is always, to a degree, present. MD will seemingly smear the doubled area away from the device impacted but it will not leave notches, how could MD leave notches? …Think about it while viewing a fictitious notching diagram of Class IV doubling going south illustrated below. While the degree of doubling is strong, there would be clear evidence of notching whereas MD would have pushed or flattened metal over the areas that display notching.


To keep on the present track, our final examples are 1909 DDO-001 and 1942S DDO-001. Like ’84 DDO-001 these DDOs have isolated doubling that is consistent in one direction. An important note is that while to a seasoned variety collector they do not look like Machine Doubling (MD), many illustrations in books and on the web, to a degree, makes it seem similar to MD as the doubling is shallow, nevertheless, there are always notching to a degree. The illustrations that follow have black arrows to show doubled areas and white arrows showing notches.

__________________

Jason Cuvelier

Let’s Talk About Doubling

This is going to be a tutorial on the 4 main types of doubling you will encounter in your searches, and how to tell them apart.

First, let me explain what a doubled die is, and what it is not.

-A doubled die occurs during the hubbing process of the dies. Up until the mid-1990s, dies were hubbed multiple times using the “multi squeeze” method. The die blank which is was to be hubbed was placed at the bottom of the “hubbing chamber”, with the working hub (depicting the image to be transferred onto the working die) sitting above it. When the chamber was activated, the working hub would descend onto the die blank with hundreds of tons of force to transfer the image. At the time, one single hubbing was not strong enough to transfer a perfect image in one squeeze, so the die was removed and put into an oven to soften the steel and allow a better design transfer for the next squeeze. Once the die is finished annealing, it is returned to the chamber for additional hubbings. HERE IS THE IMPORTANT PART. If for some reason the die and the hub are not properly aligned, when the image is again transferred, it will not line up exactly from the initial impression, resulting in a doubling of the image on the die. There are 3 main classes of doubled die directly caused by the failure of a perfect alignment between the die and the hub.

Class I (rotated): This occurs when the die and hub are lined up correctly on the X and Y axis, but the die has been rotated about its center either clockwise or counter-clockwise. Famous examples include the 1955, 1969-S, and 1972 doubled dies.
Class IV (offset): this occurs when the die is offset from the hub along the X and Y axis. Doubling will appear to go in one single direction. Famous examples include the 1983 DDR and the 1984 doubled ear.
Class V (pivoted): similar to class I doubled dies, class V only differ in that the pivot point is elsewhere on the coin besides the center. This means that the doubling will be weakest at the point of the pivot and will be strongest directly across from the pivot point. Well-known examples include the 1995P-1DO-001 (pictured below).

Since the die itself is doubled, that means that ALL COINS STRUCK BY THE DIE WILL SHOW THE SAME DOUBLING, not taking into account die state and post-strike damage.

Now, what a doubled die is NOT.
-A doubled die IS NOT a coin that is struck twice when being minted. This is a common misconception for beginners, and I admit that I thought this was what a doubled die was when I first started out.

If you wish to learn more about the hubbing process as well as additional classes of doubled dies, feel free to visit doubleddie.com for more information.

Now we will go over what to look for in your searches.
The main things you should be looking for on coins is notching and separation lines. These two indicate that the hubbing was not correctly aligned. Since there would be 2 sets of letters if we were looking at “IN GOD WE TRUST”, they would overlap at certain points and create notching at the corners.
Below is an example of 1995P-1DO-001…a class V doubled die with the pivot point around the date. This means that the doubling will be strongest opposite of the date; the motto above Lincoln’s head. The black arrows point to the notching in the letters while the red arrows point to the separation lines. I would urge anyone searching for doubled dies to purchase an example of 1995P-1DO-001 as they are inexpensive, dramatic, and will show you what to look for.


The second type of doubling you will come by, and quite possibly the one most confused for a doubled die, is machine doubling.
Machine doubling has nothing to do with the hubbing process, and takes place in the coin striking chamber. As the hammer die comes down to strike the coin, it may bounce or shift slightly if the die was installed loosely. This flattens parts of the design. This is what gives machine doubling its Flat and shelf-like appearance. A good indicator of machine doubling is if both the date and mintmark show doubling in the same direction, as doubled dies and repunched mintmarks have had nothing to do with each other up until recently. Here is an example of a machine doubled 1944-S cent. The red arrows point out the areas on doubling. Notice that the mintmark is doubled as well, and the doubling is flat and shelf-like.

The third type of doubling is most commonly found on wheat cents of the 1950s. Commonly titled a “poor man’s doubled die”, this anomaly is not a doubled die at all. Rather, it is die deterioration doubling, caused by the overuse of dies. Notice how the doubling is more ghost-like than an actual doubling of the design. The anomaly is not full like a doubled die is, and is often limited to the last digit of the date.

The last type of doubling I will go over is split-plate doubling. Found exclusively on cents with a zinc core and copper plating (all cents 1983 and on), this form of doubling can often be found on the dates of early 1990s cents, and on the reverse of many cents as well. Split -plate doubling occurs when the copper plating on the coin splits open around certain design elements, revealing the zinc below. They can be identified by the appearance of exposed zinc and a rippled appearance that is found almost exclusively at the tops of letters if you are looking on the reverse.

Sorry for the very long post, but I wanted to make sure to cover all the bases I felt needed to be covered. I hope this helps a lot of people in their coin roll searches, and that beginners will be able to more easily identify certain types of doubling.
Don’t be discouraged if you don’t find a doubled die immediately…my average is about 1 in 2500 cents if I am bankroll searching.
Remember…have fun and keep up the hunt!

Simon

 

I wanted to expand on Simon’s awesome thread here with a few more things that are often mistaken for hub doubling, but aren’t. I have recently seen several threads involving these issues and thought this would be the perfect place to add this little tutorial. These are just a few of the many examples of these and I just selected some of the more commonly noted and asked-about examples. This is by no means a comprehensive list.

First I would like to talk about what I will call design anomalies. In other words, these are things sometimes confused for hub doubling, which are really just a part of the design spanning MORE THAN ONE master hub, also called series doubling. For example:

1. The D of God had “doubled” vertical bar starting with the 1922 Master Hub and continuing until the mid 50s. I have seen this noted as part of the doubling on a doubled die, but really it is a normal part of the “design.”

2. The W in We has a strong notch on the right arm and a lesser one on the left arm beginning in 1909 and continuing all the way to 1955. Again, I have seen this noted as hub doubling, but it is normal for this span of dates.

There are others, but these were the two that I see questioned the most.

Secondly, there are many master hub anomalies confined to individual master hubs. For example, from 1937 through 1942 (excepting 1938) the R in LIBERTY had a notch on the top left corner. This is normal for all dies spawned from this master hub and is NOT the result of a doubled working die.

Thirdly, there are engraving issues on master dies, which are often confused as hub doubling. (Reused master hubs had to have the last digit or two engraved into the master die.)

1. This engraving doubling is often misconstrued as a doubled die on 1960 small date cents.

2. All 1965 cents show this notch on the 5.

3. All 1973 cents show this notch on the 3.

4. 1941 cents on the 4

5. 1944 cents on the 44

6. 1940 cents on the 40

Next, let us look at an issue many now believe to be from work done to working hubs during the 30s, 40s, and early 50.
A “trench” was added around the bust on many working hubs, perhaps in an effort to prolong the life of the working dies.
This trench is often mistaken for hub doubling. It is common for this era. It looks like this.

Additionally, we all have the doubled master dies to keep us on our toes. Please see Jason’s excellent tutorial on the 1972 doubled master die Here.

An additional example is this doubled forehead, nose, and chin seen on 1946 cents.

I am not sure what caused 1957 cents to look like this on GOD WE, but this is how the letters look on all 1957 specimens including the proofs. Here is a proof example.

Will’s Playground

Abraded Die
Acid Job
Alloy
anvil die

annealed
bay
blank

blistered plating
blank

broad strike

brass plated cent
Brockage
business strike

bust
Cast Counterfeit
clash marks
clipped planchet
collar
counter-stamp

close AM
cud
device

die break
die cap
die chip
die clash
die crack
die dent
die deterioration
die deterioration doubling
die gouge
doubled die
dual mint mark
Early Releases
edge
egg nog
feeder finger
Feeder Finger Damage
FG
field
flow lines
galvano
garage job
greasy ghost
hammer die
incuse
initials
interior die break
Janvier reduction lathe
lamination
large date
machine doubling
master hub
mini-mule
mint luster
misaligned die

misplaced mint mark

mylar
no FG
notching
over mint mark
planchet
plating
post-strike damage
progressive indirect design transfer
proof
rim
ridge ring
serifs
small date
split serif
split plate doubling
Stripped Plating
struck through
Struck Through Filled Die
third party grading service
trails
transitional design variety
upset mill
VDB
wavy steps
wide AM
Wrong Design Variety

zinc rot

Glossary List S

ABCDEFGHIJKL
MNOPQ-RSTUVWX-Z

Welcome to the Lincoln Cent Forum Glossary.
Use the alphabetical links above to navigate to the desired term.
This glossary of terms was written and compiled by Will Brooks with the help of our forum members. A huge thanks to everyone who contributed knowledge, ideas, words, and photos to make this growing educational resource possible. Special thanks to Richard Cooper, aka “Coop” who donated many of the photos.

S Mint Mark: Cents struck at the San Francisco Mint bear an S mint mark below the date. Business strike Lincolns were struck at the San Francisco Mint from 1909 until 1974, except for 1922, 1933, 1948-1951, and 1956-1967. Also, starting in 1968 and continuing to the present, proof cents also exhibit the S mint mark. One notable exception is that in 1990, some proof sets contained a cent that was missing the S mint mark. These carry a strong premium. Please see Jason Cuvelier’s excellent tutorial on S mint mark styles Here.

Saddle Strike: When a planchet is far enough off-center out of the collar that two different adjacent die pairings strike it at the same time leaving two completely separate partial strikes on the coin. There area on the coin between the two strikes sometimes buckles upward resembling a saddle.
Saddle_Strike__image_by_Jfit

Sand Cast Counterfeit: See Cast Counterfeit.

Satin Finish: The mint has made several special issues of uncirculated and proof cents that have a “satin finish.” Special preparation of the dies give these cents less glossy fields. These special satin finish issues began in 2005 and ended in 2010. There was also a 1936 proof cent issue with a satin finish.
satinfinish

Seigniorage: This is the difference in the face value of a denomination and the actual cost to produce and distribute it. This is an important issue in the debate over continuing the production of Lincoln cents, and the potential materials that may be used in their future production.

Semi-key: The “2nd tier” of difficult issues in a series to collect due to rarity and price. The very most difficult to obtain are considered key.

Series: The complete chronological run of a particular denomination or sub-denomination. For example, the Lincoln cent series runs from 1909 until the present, while the wheat cent series runs from 1909 until 1958.

Series Doubling: See Reduction Lathe Doubling.

Serif: An extension, base, or flourish often seen at the end of , and coming off at an angle to, a letter stroke. Doubled dies and re-punched mint marks can often be identified by a split in a letter’s serif.
serif

Separation Lines: See Division Lines.

SG: See Initials.

Shattered Die: A die that has suffered one or more major rim-to-rim die cracks, with some displacement showing on the coins it strikes. Some of these could be considered major retained cuds. A shattered die is unlikely to last through many more strikes before completely breaking into pieces.

Shield Cent (Shield Reverse): A Lincoln cent minted from 2010 until the present, bearing a reverse design featuring a shield. This reverse design was created by artist Lyndall Bass, and sculpted by Joseph F. Menna, both of whose initials appear on the reverse of these cents.
shieldreverse

Shifted Hub Doubling: Also called a class 9 doubled die, this is strictly isolated to the single squeeze era. It is surmised that as the pressure increases during a single-squeeze hubbing, that die can slightly shift into its final position, leaving some doubling. Since blank dies are convex, class 9 doubling usually manifests on the central design elements, especially the 6th and 7th columns on the reverse of Lincoln memorial cents, and on the left hand of Lincoln on the Formative Years in Indiana reverse.
shiftedhubdoubling2 shiftedhubdoubling

Single Squeeze: Single-squeeze hubbings began experimentally in the 1980s and became the exclusive method for hubbing dies by 1996. Before that, dies had to be hubbed multiple times to get an acceptable image on them for striking coins. By hubbing a die in a single attempt, the mint hoped to eliminate doubled dies from happening. However, this method ended up creating a new class of doubled die called shifted hub doubling, or Class 9 Doubled Dies.

Slab: The colloquial term for the plastic holder that third party grading services put coins into after grading and/or attribution. The holder will generally have the coin’s grade and/or attribution number labeled on it.
slab1

Slide-type Machine Doubling: See Machine Doubling.

Small Date: In the Lincoln cent series there are 4 years that saw a mid-year design change in the font of the date, resulting in Large Date, and Small Date issue varieties released within those years. Those years are 1960, 1970 (S mint mark only), 1974, and 1982. Please see Jason Cuvelier’s excellent tutorial on the subject Here.

Special Mint Set: From 1965-1967, the mint did not issue any proof sets. They did, however, issue these “Special Mint Sets” during those years featuring a cent, nickel, dime, quarter, and half in a plastic holder. These were not proofs, but they were struck with specially prepared dies and under higher pressure creating very well-struck coins. Coins from these sets are often called “SMS” coins.

Specimen: Any individual coin, as an example of a particular issue variety, die variety, or error.

Spiked Head: The skull region of the bust on Lincoln cents is a common area for Die Cracks to develop. See also Cracked Skull. When these die cracks extrude out of the skull into the field, they are colloquially called “Spiked Heads.” Jean Cohen lists Spike Heads in her book “Errors on the Lincoln Cent.” Photo courtesy of forum member duece2seven.
spiked head

Split Die: A die that has been bisected by a rim-to-rim die crack that extends deep enough into the die to cause lateral displacement, leaving a gap in the die, which will show as a wide unstruck raised ridge on a coin.

Split Plate Doubling (Split Line Doubling): This occurs only on copper-plated zinc cents struck from mid 1982 to the present. During the striking of plated cents, the plating is stretched in order to form the raised design elements. Whenever relief is created from a flat surface, there must be expansion of the overall surface area, thereby putting stress on the plating. Sometimes, the plating will split on the rim-side of the devices, exposing the zinc core. The exposure will be in the same shape as the design elements, thereby creating a “doubling” effect. The exposed zinc is blue-ish in color. In addition to the examples shown below, please also see Jason Cuvelier’s thread on the subject Here:
splitplatedoubling1 splitplating

Split Serif: A doubling effect on the serif of a letter as a result of hub doubling or re-punching.
splitserif

Squeeze Job: See Garage Job.

Steel Cent (Steelie): A cent minted in 1943 which had a steel core plated with zinc. This was done due to a shortage of copper during World War II. A Steel cent should weigh 2.7 grams and be strongly attracted to a magnet. A large number of these cents were re-plated outside of the mint in an effort by people to make them look uncirculated. There were also a very small number of steel cents accidentally struck in 1944. Beware of re-plated copper cents and altered cents from other years. A re-plated copper cent may stick slightly to a magnet, but not with the same strength as a genuine steel-core cent.
steelie

Stiff Die Fill Raised Design Element Doubling: See Grease Mold Doubling.

Straight Clip: See Clipped Planchet.

Strike: The moment when the dies hit the blank planchet, thereby creating the design in relief on the coin.

Strike Doubling: See Machine Doubling.

Stripped Plating: When the copper plating is removed from the zinc core of a cent using chemical or mechanical means. This seems to be a popular science experiment in recent years. One must be careful to not confuse a stripped cent with a genuine unplated cent. The former is post-strike damage, while the latter is considered a mint error. A genuine unplated uncirculated cent will still have mint luster, while a stripped one will not. Also, some of the methods for stripping a cent, such as hammering it between leather to split the plating, will leave the cent with a larger-than-normal diameter, sometimes referred to as a “Texas cent.” For more information on stripped plating vs. unplated mint errors, see Jason Cuvelier’s tutorial Here.

Struck Counterfeit: A counterfeit coin made by using dies to strike blank planchets, as opposed to a cast counterfeit, which is made by pouring metal into a mold. To identify struck counterfeits, one must be very knowledgeable of the specifications and design attributes for that issue, since struck counterfeits will exhibit flow lines and a lack of pitting, just like a legitimately struck coin would.

Struck Through: A struck-though error happens when a foreign object gets between the dies and an unstruck planchet. When the dies strike the coin, the foreign object will also be struck into it, leaving an incuse impression in the coin. The “foreign object” may be anything, such as cloth, wire, grease, dirt, metal scraps, or even another coin which had stuck to one of the dies, called a die cap.

Struck Through Filled Die: The most common form of struck through, a cent that is struck though a filled die will have missing or weak design elements. Since that portion of the die is filled or clogged with grease or dirt, that portion of the design will not be struck on the coin. Although this can affect any portion of a coin, some of the more well-known instances in the Lincoln series are the 1922 “Weak D” cents, as well as some of the “no FG” cents.
1994struckthroughfilleddie greaser

Struck Through Late Stage Die Cap This is a coin that was struck by a capped die which has already struck many other coins. The face of the die cap gets thinner and thinner with each strike, as it expands outward. After striking so many additional planchets, the face of the die cap will be thin enough to allow parts of the normal die design to appear on the struck planchets, yielding a ghost-like image of the bust and other devices. As the die cap continues to strike coins, more and more of the normal design elements will show on the struck coins until the die cap completely deteriorates away. Photos courtesy of forum member Joel.
196_ Obv.196_ Rev

Sunken Die: See Die Subsidence.

Superb (BU): A subjective term referring to the highest end of the mint state scale (MS 67+). “Gem” is higher than “Choice,” and “Superb” is higher than “Gem.”

Glossary List P

ABCDEFGHIJKL
MNOPQ-RSTUVWX-Z

Welcome to the Lincoln Cent Forum Glossary.
Use the alphabetical links above to navigate to the desired term.
This glossary of terms was written and compiled by Will Brooks with the help of our forum members. A huge thanks to everyone who contributed knowledge, ideas, words, and photos to make this growing educational resource possible. Special thanks to Richard Cooper, aka “Coop” who donated many of the photos.

Pareidolia: The phenomenon where people see patterns or objects in otherwise random data. People often “see” extra design elements that aren’t really there in a coin’s damaged areas, plating blisters, stains, etc.

Partial Collar Strike: This occurs when a coin is struck which its edge only partially contained in the collar. The part of the edge which is contained in the collar is constricted from expansion as normal, but the portion not contained in the collar expands abnormally as a broad struck coin would. This creates a bi-level edge which resembles the wheel of a railroad car, and thus these are colloquially called “railroad rims.” This is somewhat of a misnomer, however, since the edge is really the part showing the effect, more so than the rim. Photo examples pending.

Pattern Coin: A prototypical coin produced with a design that has not yet been approved for mass-production and release.

PDS System: The PDS System is a highly structured cataloging system for mint varieties and errors. It was originally compiled by Alan Herbert in 1971. PDS stands for the three main divisions of the minting process: “planchet,” “die” and “striking.” Two more divisions cover collectible modifications after the strike, as well as non-collectible post-strike modifications such as altered, counterfeit and damaged coins. Thank you to forum member 2Old for writing this entry.

Penny: A British coin with a face value of 1/100th of a pound. Also, the colloquial term commonly used for the U.S. cent.

Phantom D: In 1997, a new master hub with a D mint mark was made and used in 1997, 1998, and 1999.  A master die was made from this hub bearing the D mint mark for producing working hubs and dies for the Denver mint.  Then, the mint ground the D off of the master hub and created another master die without the D for producing Philadelphia working hubs and dies. However, the removal of the D from the master hub was not perfect and on uncirculated coins minted during these years, especially 1999, remnants of this D mint mark can be seen on the cents. It can be very faint and difficult to see, but is commonly found on cents in 1999 mint sets.  Please see Brad Podraza’s tutorial Here for further information and illustration.

Pick-up Point: Any of the specific attributes or markers on a particular variety coin used to identify the variety itself. For example, a pick-up point may be a split serif, or an elongated dot, or some other particular marker.

Pivoted Hub Doubling: Also called a class 5 doubled die, pivoted hub doubling is the result of a 2nd hubbing of a die which was rotated clockwise or counterclockwise from a pivot-point near the rim, thereby creating stronger doubling near the opposite part of the rim. This differs from a class 1 doubled die, which has its point of rotation at the center and therefore equally strong doubling around the entire rim. The 1995 1DO-001 is an excellent example of class 5 doubling. With the pivot point at K-5, there is little to no doubling visible at the date, but it is strongest near the opposite part of the rim on LIB and IN GOD. Please see Jason Cuvelier’s excellent tutorial on the subject Here.

Planchet: A modern spelling of the word planchette, which is French for “little plank.” This is the word for an unstruck metal disc, after it has had its proto-rim created in the upset mill, and before being struck into a coin. Prior to its entry into the upset mill, it is called a blank.
Blank-Planchet-plating-struck_coin_IMAGE__biokemist6

Plating: On Lincoln cents, the plating refers to the thin copper coating covering the zinc core on cents made from mid 1982 to the present, or to the thin zinc coating covering the steel core on 1943 cents. Other than this, cents were made from a solid copper-alloy. (See Alloy for compositional breakdowns) Additionally, sometimes people plate or re-plate Lincoln cents outside of the mint to give them a gold or silver or uncirculated appearance. This is considered post-strike damage.

Plating Bubbles (Blisters): See Blistered Plating.

Polishing: See Abraded Die.

Polyvinyl Chloride (PVC): A plastic which, among many other uses, is sometimes used for coin storage products, such as flips. Coins kept in vessels containing PVC will accumulate a greenish residue, ruining the coin. Take care to use materials made from mylar for long-term safe storage of your coins.

Poor: A coin grading standard of 1. See our grading guide Here.

Poor Man’s Doubled Die: See Die Deterioration Doubling.

Population Report: The number of specimens holdered by each individual third party grading service of a given coin issue or variety.

Post-mint Damage: This term is no longer preferred. Please see Post-strike Damage.

Post-strike Damage: This term is now preferred over Post Mint Damage. This is any damage that happens to a coin after the moment it is struck, including contact marks the coin may suffer before leaving the mint from falling into hoppers, or being bagged, etc. Of course, anything that happens to the coin during its life-span in circulation also falls into this category, such as purposeful or accidental hits, corrosion, unnatural toning, etc.

Pre-strike Damage: Damage to a blank or planchet that happens before it is struck by the dies.

Presidency in Washington D.C.: The fourth of four reverse design variations on 2009 Lincoln cents made to commemorate its 100th anniversary. This is also known as LP-4. This reverse was designed by Susan Gamble and sculpted by Joseph F. Menna.
PresidencyLP4

Professional Life in Illinois: The third of four reverse design variations on 2009 Lincoln cents made to commemorate its 100th anniversary. This is also known as LP-3. This reverse was designed by Joel Iskowitz, and sculpted by Don Everhart.
professionallife

Progressive Indirect Design Transfer: A form of die deterioration that manifests itself in the form of a “ghostly” image of a design element on the opposite side of a coin. The force of a die strike travels through the planchet and into the opposite die. After hundreds of thousands of strikes, the outline of the designs begin to transfer to the opposing die and show on the coins that are struck. In the case of Lincoln cents, it is common to see a ghostly outline of Lincoln’s bust on the reverse of wheat cents that are struck in later die states. It is especially visible on uncirculated coinage. This should not be confused with a die clash or a “greasy ghost.”  First photo courtesy of forum member TJ1952.

S20160130_009PIDT

Proof Coin: Unlike a business strike coin, which is used for everyday transactions and purchases, a proof coin is a specially made coin solely for collecting purposes. A proof coin is made from specially prepared dies and striking processes which result in a coin with stronger, crisper devices, sharper rim, and in the case of modern proofs, mirror-like surfaces, and frosted-looking devices. Also, since proof dies are extremely limited in the number of coins they may strike, proof coins will not exhibit the signs of die deterioration. Proof coins come in specially-made packaging from the mint.
cameo

Proof Set: A group of proof coins, usually all of the different denominations from the same year, packaged and sold by the mint for collectors.

Proof-like: This refers to a business strike coin that has unusually nice features similar to what a proof coin would have.

Proto-rim: The raised perimeter on both faces of a coin that is produced by the upset mill on a planchet before being struck. The striking process alters the shape of the rim, flattening it out.

Punch: See Mint Mark Punch. There were no date punches used in the Lincoln cent series.

Push-Type Machine Doubling: See Machine Doubling.

Glossary List M

ABCDEFGHIJKL
MNOPQ-RSTUVWX-Z

Welcome to the Lincoln Cent Forum Glossary.
Use the alphabetical links above to navigate to the desired term.
This glossary of terms was written and compiled by Will Brooks with the help of our forum members. A huge thanks to everyone who contributed knowledge, ideas, words, and photos to make this growing educational resource possible. Special thanks to Richard Cooper, aka “Coop” who donated many of the photos.

Machine Damage Doubling: See Machine Doubling.

Machine Doubling (Also Machine Damage Doubling, or Strike Doubling): This occurs when a loose die bounces (push-type machine doubling) after the initial strike and hits the planchet again in a slightly offset position, flattening a portion of an already struck device, creating a “shelf-like” doubling effect that cuts into the normal size of the device. This is often misconstrued as a doubled die by novices, but is common and essentially worthless. Sometimes the die will “slide” rather than bounce, creating a smeared look to the devices. (slide-type machine doubling). Ejection doubling is another form of machine doubling where the coin “sticks” to the anvil die when being ejected from the striking chamber. In addition to the examples below, please see Jason Cuvelier’s excellent tutorial Here.
1955pluralpluribusslidemachine doublingslidetypeMD

Marker: A die-specific attribute used to identify a particular die, and useful for confirming a particular die variety. A marker can be many things from a mint mark’s position to a die crack or die chip, die scratches, die clash remnants, cuds, etc., all of which are unique to each die.

Master Die: The die that is made from the master hub. The master die is then used to create many working hubs, which in turn each create many working dies, from which coins are struck. Master dies often had to have the last 2 or 3 digits of the date engraved into them, so that the master hubs could be re-used in multiple years. These engraved portions often had anomalies and imperfections that would show up on each working hub and working die spawned from the master die. These anomalies are sometimes confused with hub doubling by novices. A master die could also be itself a doubled die. (See Master Die Doubling.)

Master Die Doubling: When a master die is itself a doubled die, (or exhibits another type of doubling such as engraving doubling) each working hub and subsequent working die created from this master die will also show this doubling. Since a doubled master die creates many working hubs and dies, this doubling will be very common, if not universal, during a specific year, and is therefore not a collectible form of doubling. There are many years in the Lincoln cent series exhibit master die doubling, with 1972 being the most well-known and most often mis-attributed as a collectible doubled die. 1972 had 2 master dies. One exhibited doubling and one did not. Therefore at least half of all 1972 cents will show this master die doubling. For more detailed information on the 1972 doubled master die please see Jason Cuvelier’s tutorial Here.  See also: Engraving Doubling.

Master Hub: A master hub is the original steel rod that holds the design for a coin. In the past, the master hub was created by using a reduction lathe that would engrave the design onto the hub from a galvano. The hub would have raised design elements on it, just like a struck coin has. The master hub would then be squeezed onto another blank steel rod creating that design in reverse relief. This would be the master die. In modern times, the master hub is created by transferring designs directly from a computer image. The master hub often was created without portions of the date on it, so it could be re-used in subsequent years. The missing parts were then engraved into the master die for that year.

Matte Proof: A French method for making proof coinage. Matte Proof Lincoln cents were struck from 1909-1916. Extra striking pressure and multiple strikes created extra-sharp details on these cents. These coins also exhibit sharply squared-off rim. The dies used for making these proofs were sand-blasted, as a way of polishing the die, so matte proofs also exhibit a textured grainy surface as a result of this practice. Matte Proof Lincolns had extremely low mintages and carry large premiums.  Image from Heritage Auction Galleries.
1915 matte proof obv2

Memorial Cent (Reverse): A Lincoln cent struck from 1959 until 2008, exhibiting the Lincoln Memorial on the reverse. This reverse was designed by Frank Gasparro, the 10th chief engraver of the U.S. Mint. His initials, FG, show at the bottom right of the memorial building on these cents.
memorialreverse

Mid Die State: Cents struck in the middle of a die’s life-span. These cents will exhibit some signs of die deterioration, such as radial flow lines, and earlier stages of die cracks, die chips, etc.

Mid-Year Design Change: In the Lincoln cents series, there were several dates that saw an intentional change in design during the year. Some examples would be 1909 cents with and without the VDB, 2009 cents with 4 different reverse designs, and all of the years with both a large date and small date.(1960, 1970S, 1974, 1982)

Mini-mule: A coin with a wrong design on one side, but still appropriate for the denomination. For example, in the Lincoln cent series, these refer to the transitional design varieties and wrong design varieties. These coins exhibit reverse designs intended for other years, even though they are all memorial reverses.

Mint: The place where U.S. Coins are struck. Most Lincoln cents were struck at the Philadelphia, Denver, or San Francisco mints; however, between 1974 and 1986, some Lincoln cents were struck at the West Point mint. These cents also did not bear a mint mark, making them indistinguishable from those minted in Philadelphia. The word “mint” can also refer to the condition of a coin.

Mint Luster: The reflective qualities of a newly struck coin. The flow of metal toward the rim from the striking process creates tiny radial flow lines that reflect light. As a lustrous coin is tilted under light, the reflected light will appear to move around the coin. This is called “Cartwheel Luster.”  This cent below exhibits cartwheel mint luster. Photo donated by RLM’s Cents.
68O

Mint Mark: A letter or letters that appear on a coin designating which mint struck the coin. On Lincoln cents, coins struck at the Philadelphia Mint have no mint mark. Cents struck at the Denver Mint bear a D below the date, and cents struck at the San Francisco mint bear an S below the date. For business strikes, mint marks were punch by hand into the working dies through 1989, thereby creating variance in position, orientation, depth of punch, and even re-punchings. In 1990, the mint mark became part of the master die for business strikes, putting an end to the aforementioned variations. For proof strikes, the practice of hand-punching mint marks into the working dies ceased in 1985.

Mint Mark Punch: The device used to add the mint mark to the working dies. The mint mark was punched by hand into the working dies for business strike Lincoln cents up through 1989. Starting in 1990, the mint mark was part of the master die, so punches were no longer used. For proof coinage, the practice of hand-punching the mint marks into the working dies stopped in 1985.

Mint Mark Style: Over the years, the font of mint marks changed many times. Commonly used “MMS#s” are proprietary to varietyvista.com. See D Mint Mark and S Mint Mark entries to see these variations.

Mint Set: A group of uncirculated coins packaged by the mint and released to collectors.

Mint State: A grading standard of 60-70. See our grading guide Here.

Mintage: The number of coins struck of any particular mint issue.

Misaligned Die: This refers to a coin that was struck by dies that were not in correct position in relation to each other. A coin struck by a misaligned die can be determined by noting a difference in its relative centered-ness between the obverse and reverse of a coin. Below is an example of a cent struck by slightly misaligned dies.  These do not command a premium unless the misalignment is severe enough to have part of the design cut off.  Photos courtesy of historyhound.
MAD2 MAD1

Misaligned Die Clash: A misaligned die clash is a die clash that happens with dies that are not properly lined up with each other. Clash remnants from these events can be rotated, offset, or even pivoted from the normal position. There was a sudden increase in these that occurred in the 1990s.

Misplaced Mint Mark: A mint mark that is punched into the die in an area outside of its normal location. On Lincoln cents, anything in the field below the date is considered acceptable. Many of these supposed misplaced mint marks are disagreed upon by experts. Some publications list what are most likely die chips in the date as misplaced mint marks. Others, like the 1958D 1MM-021, which has supposed punchings in the vest area, are still debated. 1953D 1MM-033 is a nice example of a D tilted and lightly punched into the vest area. It can be seen Here at coppercoins.com.

Modified Hub Doubling: Also called a class 7 doubled die, modified hub doubling occurs when a hub is altered in between hubbings of a die, or when a die is hubbed with one normal hub and one altered hub. This alteration can be intentional, like the grinding off of an element, or it can be accidental, like a piece of the hub breaking off. An example of class 7 doubling in the Lincoln cent series occurs in 1941, where we see many different dies exhibiting both a normal and a “broken” 2nd T of TRUST on the same die.
1941brokenT1 1941bokenTcoin2a

Motto: On a Lincoln cent, as well as other coinage, the motto almost always refers to “IN GOD WE TRUST,” although LIBERTY and E PLURIBUS UNUM are also technically mottos.

Mule: This is a coin which has mismatched obverse and reverse designs, not normally found on the same issue, such as the 2000 Sacagawea dollar/Washington quarter mule. Other than the transitional design and wrong designwide AM,” “close AM,” and “1988 RDV-006mini-mules, the only known major mule in the Lincoln series is a lone specimen of a 1959D with wheat reverse, which the mint has confirmed as genuine.

Mylar: A brand name for a clear polyester film used for, among other things, safe, long-term storage products for coins.