Who knows for sure why someone would do that but the 1964 Nickel is one of the most minted ever for the Jefferson series. Perhaps someone thought it would be a nice choice for an experiment. Either way it makes me
Might not have been intentional. I know that acid dipped cents were common to reduce the size so they would work in parking meters and vending machines a few years ago. And acid is used for a lot of things, so who can say.