A foldover strike occurs when a planchet or coin is struck on edge and folds from the impact. The error, however, appears to have become obsolete.

The average coinage die lasts about a day, intact. Eventually though, damage begins to show. Repairs abrade design elements; machine parts also scuff dies.

Collectors' Clearinghouse explains: Clipped discs can leave characteristic impressions in coins.

Grading error coins can be a challenge, even for experienced graders at third-party grading services.

The surface of planchets and coins can sometimes peel and crack. These defects are known in the hobby as “lamination errors."

Every so often a coin is struck on a planchet whose specifications deviate markedly from normal. Some are experimental strikes; others are errors.

The blank surface of uniface pattern test strikes can reflect the presence of a metal block, an underlying planchet, or a smooth, flat-faced die.

Once in hand, a coin purchased as a gamble on eBay proved more interesting than the buyer could have imagined.

Even though die errors are repetitive in nature, many noteworthy die errors are represented by only one or two examples.

Any elevation at the perimeter of a coin or planchet might be said to be a "rim." Two kinds are designed rims; others are errors.