Struck Through
The image to the left is an example of a 1960 D
Lincoln Cent that was struck through some foreign
object.

A struck through error is caused by a object being
between the die and planchet at the time of
striking.  Objects can range from staples, to
grease, to wires, to cloth, or any object found at
the mint.  

See also,
struck thru die cap errors.  

Images courtesy of Jean K