With little to lose I would let the IH soak in 'Go-Jo' for a
few hours. Use a wood toothpick on the corrosion. Don't
leave it overnight. Instead let it set in a plastic bottlecap
with dishwater liquid soap diluted in soft water. Distilled
water is safest. Next day get another bottlecap and let
soak in 'Go-Jo' for a couple hours. Check the coin and
use a toothpick to gently prod the corrosion off.
I have used this method on badly stained ugly coppers
with mixed results. It won't hurt the coin if you monitor
closely. Too long in the hand cleaner will remove the aged
appearance.
Go-Jo is amazing at refinishing dulled furniture while
protecting the wood. I never use strong solvents on good
antique wood since discovering this procuct.
If you have time to carefully watch the coin you can get
most of the stains off coppers using Go-Jo, not the other
similar hand cleaner which has no lanolin.
lastleg