2017-P Nickel Dryer Damage

Acid or maybe heat.
John1

It was alter post strike. On another coin that looked similar to this one, you can see the reverse die was in really bad shape:

But notice one thing that doesn't look like the die issue? Note the rim. The rim is normal. That tells me it is a die issue, and not an altered coin. On this coin (OP's) note the the rim is also affected. So this tells me it is not a die issue (die event). But an alteration of the coin.