Well a struck through error is incorrect. Why? When a die fills with grease, it makes the devices wider.


In this case the devices are smaller than normal. So it is the result of a polished die.


This coin is a 1964 proof cent reverse. Seems like 6,000 strikes to a die was too many for this die. (possible die damage was the issue)
Same even on this OP's coin. The edge of the die was over polished so much that part of the devices went away.