1955 double die
The 1955 double die is a minting error that occurred during production of the one cent coin at the United States Mint, in 1955. An error in the minting process caused a small (but notable) number of coins to be struck in such a manner that the year 1955 appears twice on the coin, with one "1955" slightly overlapping the other. Other parts of the lettering also show doubling.
The 1955 double die is one of the most famous error coins. It is well-known and collectible enough for genuine double die coins to fetch prices in the hundreds of dollars, depending on condition.
The same error that produced the 1955 double die also caused a large number of coins to be struck with a partial overlapping date, with one or more digits of the "1955" appearing twice on the coin. This error is known as the "poor man's double die." It is much more common than the actual double die, and as such it sells for only a few dollars.
