Coin Collecting - Proof and Error CoinsProofs and errors are two-sides of the same coin, so to speak. A proof is a coin made as a prototype to test a design. They are made in limited quantities and so, sometimes much later, become highly valuable. Since they are usually as near pristine as a coin can get, their condition makes them worth more even when new. But sometimes the proofing process goes awry. Errors are coins that were minted with some kind of flaw. Because of the mechanics of minting proofs, several types of error have been relatively common. Double-striking is a technique used to make proofs that have very prominent features, but unless the registration is perfect it can result in a 'shadow'. Blank or planchet errors occur when the metal disk intended for striking (the planchet) remains blank. There are two types, one in which the rim has not yet been raised on the coin, the other when it has. Even though the coin has no currency value, it can still be prized by collectors. Planchets are sometimes struck with the wrong denomination. A blank of the size and composition used for a dime might be struck with the look of a nickel. Some U.S. denominations have even been struck on foreign planchets. They're considered very valuable, owing to their rarity. A brockage error occurs when the obverse (the 'face') and reverse ('back') of the coin are struck with incorrect images. The obverse design can be struck on the reverse of the coin. The obverse image of one die and the reverse image of another die can wind up on the same planchet. These are 'mule' coins, with one of the more famous being the Sacagawea Dollar/Washington Quarter. These are rare collectibles. Several different types of die error can occur. The 'die' are the pieces, top and bottom, that are etched or engraved with the negative image that will produce a positive image on the coin. The planchet resides between two die and is struck to impress the images. Like any metal piece, dies can be defective. A crack can open in the die, yet remain undetected. Coins struck with a cracked die show a distinctive mark. Some Morgan Dollars series are well-known for showing die cracks. Collar die errors occur when the circular die above the anvil (the lower) die malfunctions. Off-center coins are produced when the planchet doesn't sit properly in the press. When struck, the image is askew. These are relatively rare, and hence sometimes valuable. Mintmark errors result when the letter designating one mint (say P – Philadephia) is struck onto a coin minted in another city (such as Carson City – CC). This can increase the value of an otherwise ordinary coin. Though mints today have extraordinary quality control, in earlier centuries processes had not yet developed to their current state. Therefore, most errors are going to be found among older coins, already valuable in part because of their age. If you have a newer coin with an error, have it checked to ensure it's not a fake.
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