Someone dumped a grimy quarter in change on me today. So black encrusted I couldn't even see the date. Took it home, washed some of it off under the faucet, and saw it was dated 1953. 90% silver.
Did the trick with aluminum foil and baking powder to get the rest of the tarnish off and now it's nice and shiny like new. I wonder where it's been all this time.