Just wondering what type of error this would be classified as. The only thing I can think of is a defective planchet. I appreciate any thoughts you may have on this. Thank you!
Possibly, but I think it might have been a stray piece of metal caught on the planchet when the coin was stamped, then fell off ?
Looks like a struck through. As 10gary22 says, it was a piece of debris (wire or ?) that was struck and fell off. Here's a pic with a cent still with a piece of debris retained:
