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!
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.
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.