Common coin errors
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An error coin is a coin that is minted abnormally. Many different types of errors can occur during the minting process. The following are some of the most common error types.
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[edit] Numismatic Value of Error Coins
Most error coins demand a premium when sold, if they are modern coins, dependent upon the rarity of the type of error as well as the rarity of that type of error on a particular denomination. The value of error coins has been subject to much debate and the value is usually determined between the dealer and the collector. Conversely, errors on ancient, medieval and higher value coins are usually detrimental to the coins numismatic value.
[edit] Blank or planchet
This is simply a planchet intended for coinage but not struck with a die. In the process of minting, planchets are first struck from strips of thin metal. A planchet on which the rims have not been milled upward is more valuable than a processed planchet. Note: The rim on a blank is not raised, while the rim on a planchet is raised.
[edit] Defective Die
A coin shows a break on its surface. This is caused by a crack in the die used to strike the planchet. Coins sometimes show an unstruck area resulting from a break in the die. This is known as a cud mark. In U.S. coinage, many coins from the Morgan dollar series show slight die cracks.
[edit] Lamination
A coinage defect consisting of a portion of the metal separating from the rest due to impurities or internal stresses. Lamination flaws occur primarily when a foreign material or gas oxide becomes trapped within a die. This error common with clad or plated coinage.
[edit] Off Center
This error occurs when the coin has been struck outside of the planchet, due to the planchet improperly entering the coinage press.
[edit] Broadstrike
Broadstrike errors are produced when the collar die malfunctions. The collar is the circular die surrounding the anvil (lower) die. It applies the edge device (reeded edge, plain edge) and prevents the metal of the coin being struck from flowing outside of the confines of the die. When the collar is prevented from working properly during striking, it may rest below the surface of the anvil die. All denominations of U.S. coins with a broadstrike have a plain edge.
[edit] Clipped Planchet
Occasionally a misfeed can occur where a strip isn't fed through far enough. When this happens, the punches strike an area of the strip which overlaps the hole left by the previous strike. The result is a blank with a piece missing. A clipped planchet is straight, curved, ragged, incomplete, or elliptical.
[edit] Wrong Planchet
This occurs when a denomination is struck on a planchet of a different denomination. Some examples include cents struck on dime planchets, nickels on cent planchets, or quarters on dime planchets. Sacagawea dollars have been reported with statehood quarter designs on the reverse. A much rarer error is a U.S denomination struck on a foreign planchet (17th,18th, and 19th centuries only).
[edit] Brockage
A mirror image of a coin has been struck on both sides of the planchet. This error typically occurs when a coin remains on either die after striking. The second coin receives the image from the die, though its blank other side also receives the image of the struck coin. The result is an incuse mirror image, and the coin is known as a brockage error.
[edit] Multiple Strike
This occurs when the coin has an additional image on one side from being struck again, off center. The coin will not be of a normal shape. Note: Also referred to as 'double exposure.'
[edit] Overstrike
In the past, it was a common practice for a mint to use a certain die until it broke. As some dies would last for multiple years, a figure would be punched over the old date. For example, some 1942 Mercury dimes show a 1 beneath the 2.
