Since the use of coin "milling" machines coins tend to be of a uniformed size and shape.
When a coin is produced a blank coin planchet is fed into a collar. The collar surrounds
the planchet as the dies strike it, and the planchet is squeezed against the collar and
dies, leaving the shape and design of the coin.
If the collar is not fitted or it is miss-aligned then the coin produced will be out of shape.
This type of coin is reffered to as a Broadstrike.
1966 Broadstruck Half Crown
|Courtesy of Jeremy Katz