Modern coin minting is a highly technological process. On occasion however, even the most advanced processes break down, and mistakes are made.
Errors in coin manufacturing are manifested in a number of different ways, the most documented of which are detailed here:
- Planchet Errors: The planchet error occurs when the wrong planchet (coin blank) is fed into the coin-striking press. What results is the incorrect design appearing on a particular coin. Examples of this include cent artwork appearing on dime pieces or quarters on dimes.
Strike Errors: Strike errors are caused
by a flaw or malfunction in the press machinery. The two most common examples of
strike error are:
- Broadstrike: This happens when the collar piece, that is, the part of the press responsible for the maintaining the shape and size of the coin during the strike is damaged or missing, causing either the edges of the coin to be flawed or the dimension of the coin to be irregular.
- Misfeed: As the name implies, misfeeds are the result of the planchet not having been properly inserted into the press. If not perfectly aligned, strikes may occur in positions on the planchet not intended to be struck or on the edges of a previous strike, resulting in “clipped” coins. Such examples can be identified by their missing portion of the coin.
- Defective Die: The “die” is the portion of the press responsible for striking the image into the planchet. It is comprised of hardened steel and contains the image (in reverse) intended to appear on the finished coin. Throughout the course of their usage, die can become worn or damaged. Coins minted using defective die can be easily identified as they will have either a raised line across their surface, resulting from a crack in the die or missing artwork altogether stemming from a completely broken die.
- Brockage: Brockage errors usually result from a coin sticking to its die after the strike. What results from each strike until the problem is remedied is a coin with identical images, with one concave instead of convex, on both sides.
- Overdate: In the past, it was common to use a die until it broke. Because they could last for several years, it became necessary to change the date on the coin after it was minted. To do this, minters simply struck the coin again with a new number over the last digit in the date. What resulted was a coin that could be seen to have two numbers in same position on the coin.
“Error Coins,” as the coins resulting from the above mistakes in striking are collectively known, have a numismatic market all their own. Because these errors, especially in modern minting, are extremely rare, coins which contain them are valued at a high price – often above other rare coins.