Split Planchet
The coin to the left is an example of a split
planchet.  Planchets can split before or after the
coin is struck.  The example to the left was split
after the strike.   

A split cent planchet is usually the result of deep
laminations due to poorly mixed metals or

If a coin splits after striking, the result is usually a
coin that is fully struck on one side, and may or
may not show a phantom strike on the other due to

If a coin splits before striking, the result is usually a
weakly struck coin due to the fact that the split
planchet is too thin to fill the space between the

Image courtesy of iwork4coin.