*REALLY BAD* PMD... like "I have a blow torch/beaker of acid and I wonder what it would do to this coin" kind of PMD.
Yeah, I had to. There is always that little voice in the back of my head that wants to make sure it's not some strange error that I don't know about. Thanks ;-)
The only thing I find strange is that you did ask. Lol. melt it or use the acid, either way should be an improvement.
Coins with that look are chilling to me. I think it was in a serious house fire, hot enough to begin melting the coin and expand a plating bubble on it, without fire actually directly touching the coin since it's not darkened. A torch would probably show more localized damage, and acid would noticeably lower the weight of the coin.