Assorted mishaps can leave a coin with an island of die-struck design marooned in the middle of an otherwise unstruck surface.

There are many quality control steps between the artist’s original conception of a coin’s design and the release of that coin into general circulation.

Encrustations can form in the bowels of the press. Any lubricated joint or surface is a magnet for dust, dirt that can later loosen and fall between the dies.

The edge of a newly-struck coin is flat and vertical. However, certain errors will leave the edge with an overhanging lip or a slanted cross-sectional profile.

A counterbrockage is a raised, normally oriented version of the design that is produced when a brockaged coin is struck into a planchet.

As with any denomination, cent weights will vary, with some falling above or below the mean.

A die cap is a coin that sticks to a die and strikes a succession of planchets.

I recently encountered my first foreign edge strike in the form of an undated aluminum India 10-paise coin with a design that was minted between 1983 and 1993.

When partial breakage instead takes place in the vertical plane or along a steeply oblique plane, the defect is designated a “cracked planchet.”

For most coins, production ends with the strike. But Presidential and Native American dollars go through an additional step that generates the edge design.