Illinois numismatist Mike Diamond has a firm grounding in the scientific method, having taught college-level evolutionary biology and anthropology.

A blank or struck coin can split along a horizontal plane, from a poorly mixed or impure alloy. Clues tell whether the pieces split before or after the strike.

Indian 1-rupee coin has combination of die alignment problems: vertical misalignment, horizontal misalignment and a rotated die error.

A die clash occurs when minimum die clearance drops to zero and the dies collide when a planchet fails to be fed into the striking chamber.

Rotational machine doubling is caused by an unstable die rotating around a central axis after the initial impact.

What at first appeared to be a centered double strike to Coin World columnist Mike Diamond was actually a different, very rare error.

An unconfined planchet that is perfectly centered when struck becomes an oversized coin known as a broadstrike, sometimes called a “centered broadstrike.”

This five-cent coin is one of many that have been damaged while being minted.

Newcomers often ask if their clips, or incomplete planchet coins, are genuine. Determining authenticity is a snap once you know the four key diagnostics.

A 2000-D Lincoln cent and a 1983 Jefferson 5-cent coin are included in this week's Coin World Collectors' Clearinghouse column.