Struck Through Cloth
The image to the left is an example of
a Lincoln Cent that was completely
struck through cloth on one side.

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.  

Notice the textile pattern on the coin.  
This identifies it as struck through

Images courtesy of Brian Balise