Coins that are manufactured erroneously (error coins) are quite fascinating. There are many varieties including off center struck coins, coins that show mechanical doubling, die breaks, indents, struck through errors, coins with curved or clipped planchets, double die coins, and coins with missing lettering just to name a few. Every collector should have at least a couple examples in their collection. Not only does it make for a well rounded collection, but it is very informative as to the actual minting process. Most errors never make it it into circulation because they are usually caught at the mint and melted. But when they do happen to slip by, this not only makes them rare, but also a real surprise if you find one in your change!