Weak strike - Errors and varieties
There are several reasons that can cause this error. When a new die is put in place, tests are made for, among other things, die clearance and approximation to check if the dies approach each other closely enough to leave a strong impression. Normally, these test coins (also called die adjustment strike) are normally sent to be melt and are not supposed to be found in circulation. A die adjustment strike will show a poorly developed or absent design rim.
Even if the pressure is perfect, incomplete relief on a coin can also be because the blank wasn't heated enough before the strike.
A weak strike could also be due to a loose or cracked press frame, a loose or broken knuckle joint, a mistimed anvil or hammer die, a broken cam associated with either die, a jam-up in the guts of the press, a jam-up associated with an adjacent die pair, a broken circuit breaker, or simply dies that have fallen out of adjustment.
Weak Strike values
Only in very rare instances, like when it affects the overall of a coin, weak strike might worth a bit more than a regular coin.