I sprayed a '64 Kennedy in about 1966 with acrylic laqure from a spray can for an amusement. That coin is still as fresh as the day I sprayed it.
Actually, I treated three of them. The laquer tended to peel off, so I re treated just one, and put it in a Mylar 2x2, then into a PVC album page, where it remained until recently. Now in an archival quality page.