Since it has no value then would lemon juice clan it just so I can have it shining in a Mylar holder?
You'd have better luck with acetone (pure, not nail polish remover), but only if you know how to use it. If you don't know how to use acetone, leave the coin as is.
Silver often has a tendency to turn black when it is subjected to environmental conditions. Yes, acetone would be the best thing to use, and since the melt value is just under $1.50, it just might be the best coin to use for experimental purposes. Chris