Info For New Members- Doubled Dies
If anyone would like to add anything to this post, please chime in. I'm going to do the best that I can with this, and am going to hopefully have this post inform any new members so they don't flood the boards with posts.
Brief minting process overview as it relates to doubled dies: All designs are first created by a designer using oftentimes a plaster or similar model, where rubber and and epoxy inverses are made. These are large diameter models, so they must be reduced. As such, they are then transferred to a Janvier lathe that will transfer the design at a smaller scale into a master hub (correct image). This is pressed multiple times into blank die steel rods which creates a master die (inverse image).
After this, the master die is pressed multiple times in the hubbing press at high pressure into a blank steel rod and this forms a working hub (correct image). Then these working hubs, of which multiple are created, will be used in the hubbing press to create working dies (inverse image) by multiple strikes at high pressure into a blank die steel rod. The die had to be heated before each strike, which will lead us to how doubling occurred.
At any point during these processes of pressing into a blank die steel rod, doubling can occur. Any doubling that occurs during the master or hub part of die making will result on thousands of coins, or all coins created. This is called hub doubling and is found on some coin series, an example would be the 1964 Accented Hair halves.
The most common doubling occurs in the last step, where working hubs are pressed multiple times into blank die steel rods to make working dies. This is where the doubling collectors look for occurs. It will show on the coin as a wider letter or number with SPLIT SERIFS and raised devices where the doubling is. This is caused by the die having to be removed from the hubbing press before each strike, often two or three times. If the hub and die were misaligned during any subsequent strike in the hubbing press, doubling occurred.
Here is an image showing how true doubling looks, this is not mine but someone posted this a while back, I can't remember who:
There are many different forms of worthless doubling, but two of the most common types are machine doubling (MD) and die deterioration doubling (DDD). These appear as the flat, shelflike doubling that is seen on the top left picture. This is created when a die in the press is loose and the die moves ever so slightly during striking, shearing some of the design flatter. This occurs on millions of coins and is worthless.
Modern coins are now made by use of a single press hubbing press, so the doubling that occurs on modern coins is very slight and carries very little premium, if any at all. It is nearly impossible to see so many collectors don't want those coins.
The best way to identify if your coin has doubling is to go to Variety Vista (http://www.varietyvista.com ) and find the date and denomination of your coin, and see if it matches one of the listings there. Let me make myself as clear as I can when I say ALL parts of the coin must match EXACTLY. There's no, "oh it looks close" because the coins with doubling all came from the same die so there is no such thing as close. It's either exact or you have a form of worthless doubling.
If you think you have found an unlisted variety because your exact form of doubling isn't listed on Variety Vista, then you are likely wrong. Many new collectors don't have the understanding of the minting process to identify a new doubled die, and these new discoveries are becoming exceedingly rarer. The chances of you actually having one are lower than winning the lottery. It just doesn't happen more than a few times a year, and major doubled dies (valuable ones) are identified right away.
Hope this helps, and happy hunting! Remember, check Variety Vista!
Young Numismatist, Coin Photography: https://forums.collectors.com/discussion/1090140/flyingal-coin-photography-10-photos#latest