How could one, by any stretch of the imagination, think this an "error" coin? I do not mean to sound harsh, but even to one wholly unfamiliar; common sense should dictate that such a thing was much more likely done by a person rather than a mistake by the mint.
Simple. If they have no clue then all sorts of things can be imagined. There are two things that most of these folks know for sure. 1. Error coins can sell for a LOT of money. 2. Their particular coin looks "different".
Of course... all boils down to seeing what one wants to see. No reason to spend even a moment to actually think about it when there is a hope and a dream. On the other hand, I can probably relate... when the wife and daughter come home looking "different", all that I know for sure is that it cost me a LOT of money and oh how I wish it were all just some kind of "error".
No it wouldn't. Pure acetone is a universal solvent, and it will not alter the coin in any way(other than removing the nail polish.) However, you can dip this coin in acid if you want, and it will not lose a single bit of its 5 cent value.