Possible 1892 Columbian Exposition Half Dollar Lamination Error On Reverse

It is 90% silver, and as far as I know, was not a dug up coin and 90% silver wouldn't corrode like that. Research lamination errors and you will see what I mean looks just like any of those examples.

Yeah, I have no clue just kind of basing it off random pics of lamination errors. It seems odd that this would corrode though, being 90% silver. What else could cause this kind of post mint damage?

Yeah the more I have looked into this seems to be the case, but who would have dropped acid on this coin for no reason back in the day? Its been in the family I got it from since a 65 yr olds dad had it who has been dead for close to 15-20 yrs , so it is not a dug coin, and it's not been purposely damaged. What in the F is it? The pics are odd, maybe I should scan it? It is highly unlikely to have been altered with chemicals, look at the globes, if you dropped anything between them it would have affected both of them, and as you can see its clearly just on the right globe. Any advice?

I'm not an expert on these but 2 things strike me. First, these were originally meant to be sold as a souvenir so it'd would seem weird to me that such an error would leave the mint. Second, the damage to the right of the ship almost looks like a series of round punches.