Let's talk about doubling

[simonm]

Posted this over on cointalk the other day and thought I might as well post it here, too.

Hi all.
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

[cimperialis]

Nice post, Simon. I don't think there can be too many educative posts on doubling like this. Fantastic for beginners and even intermediates.

[amnight]

Thanks for the write up Simon. It is really informative!

[pennies4pennies]

Very well said Simon. This very well needed for beginners. I must say I first thought when I started out that a doubled die was being struck twice. Later I found out I was wrong. I can almost bet that everybody here at one time thought the same thing when they started off. Not unless you are Bob / he was born knowing

[cimperialis]

Is this a sticky yet?? Much more useful than some of the others...

[simonm]

I could make it a sticky if you guys want. I know there are threads regarding each type of doubling individually, but I think this is one that compares the 4 main types of doubling all in one thread. (I did see a few ones where Jason nailed I think 3/4 types of doubling in one thread.)

[MrHaz78]

Great job Simon. I actually found an example of the 1953 you used in your post just last week. Bill

[teryble]

How common is Machine doubling Simon?

[simonm]

How common is Machine doubling Simon?

Fairly common. You will see it is very abundant 1969-1972.

[celartu]

Excellent information, good to learn a lot of cents