Acetone

Acetone is known to have no effects on coins or any metals. I've experimented with attempts to see if allowing coins to sit in Acetone for days, weeks or even months would effect the coins. I can not remember the total coins but there was a cent(penny for us that know what that is), Nickel, two Dimes and a quarter. After several weeks in the shade, in the sun, indoors and outside, I could see no difference from when I started except one Dime did look cleaner.
Of course I can not predict what would happen if you placed coins in Acetone for several hundred years. You could try that and get back to us for the results in about that time frame.

Actually when people find coins on the ground or in dirt I always suggest first trying distilled water. The warmer, the better. Not boiling, just warmed. Usually if the coin is just dirty, and I mean with dirt, distilled water may absorb that dirt. Anything left then may work with the Acetone.
If these don't work, the best thing is to leave well enough alone.

Regardless of the possible results remember that ANY oil placed on a coin will leave a film. Such films must be removed so then your back to Acetone or other chemicals and then usually to rinse with distilled water to remove any possible residues. By now you have a cleaned coin.