I'm not an expert, but it looks like a minting error, not post-mint damage. The deformity goes 'under' the struck pattern of the coin, it doesn't eat away the pattern, which would be the case with post-mint damage.

We have a couple of examples, with approximate values and references for further research, of 'struck through' error coins. It looks like yours is 'struck through foreign material.'

https://coinquest.com/cgi-bin/cq/coins.pl?coin=1422

https://coinquest.com/cgi-bin/cq/coins.pl?coin=2713