Try using a scanner too and scan at 800 dpi. It's too bad most FE cents do not come out of the ground well (my '57 included). I don't think the estimates of $5K posted earlier are accurate for this coin--I don't believe this coin will grade due to the environmental damage, though if it is a '56 it would prossibly bring up to a couple hundred bucks or so. Regardless of the date any FE is a great find....congrats on it AND the half dime--sounds like you got yourself a good spot there! Personally I wouldn't sell it--put it in a nice plastic case after sealing it and just add this rare coin to your collection.
As Grant mentioned, don't attempt to clean the coin any more.