Die deterioration doubling
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Die deterioration doubling is an extremely common form of mint-made error on many United States and Canadian coins that results from degradation of the die used to strike the coin.
Due to a combination of improper preparation and treatment of the dies, excessive wear, and overuse, die deterioration doubling has occurred on nearly every series issued by the US mint in recent times. Certain coins are more susceptible to it than others, due to various factors, but it does occur on most series of coins.
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[edit] Identification
Die deterioration doubling is a result of a few simple causes, but it can be difficult to positively identify. There are a number of different features which appear similar, but the characteristic traits of each are easy to identify with practice. Die deterioration doubling is often mistaken for hub doubling. The causes of the two types of doubling are different, but their appearance on the finished coin is often similar. Die deterioration doubling appears most often around the mintmark and date because they are alone in the field. When it occurs in other features, like an image of a bust, it looks more like a weak strike than doubling.
Close examination of affected features show that the doubling is extremely irregular. This is because the coin metal does not flow from just one direction, but flows and produces wear on the die from all sides. There is no definite shape, and it can take on several different but similar appearances. It often looks like a thin metal shelf or spreading spot. It can also make lettering appear thick and twisted. There are no crisp lines affected, but things generally look bloated, enlarged, blurry, twisted, and damaged. This is different from hub doubling, because hub doubling appears as a crisp secondary image, rotated minutely from the original. When casually glancing at a coin, the difference is not easy to tell, but when magnified, the difference is obvious on most coins. Another easy way to tell hub doubling from die deterioration doubling is the presence of notched serifs; the small flairs on the ends of letters will appear distinctly separated with the former, whereas they appear just blurry and washed out with the latter.
[edit] Numismatic Interest
Many beginning numismatists buy coins thinking they are very valuable, but really are not worth more than a little over face value due to a die deterioration doubling. This common error fools a number of people into believing that it is a much rarer, and more valuable, form of doubling. It goes by a number of names, such as the "poorman’s double die."
Jefferson nickels and Lincoln cents especially exhibit a large number of affected coins, throughout the entire history of the coin. The 1955 "poorman’s double die" is actually outside abraded die doubling, and a high percentage of 1999 coins exhibit this error. Because of the large numbers of these coins in circulation, they are not worth more than a few cents over normal value. Nevertheless, die deterioration doubling can deceive the beginning numismatist with the high hopes of discovering a new variety and making a fortune.
