Some time ago I had some coins that were all messed up one way or another. The nickels were polished to a mirror like finish. The Large Cent
was corroded, stained, potted with stuff like yours. One Lincoln, the 1919 also was covered with something. The Indian Head was really full of something green and black.
All were placed in the same glass jar for a while with Olive Oil. Eventually all were dumped in Laquer Thinner for a few days or more. Not sure. Then rinsed with Alcohol and placed in a clean jar of Acetone and left on a picnic table for a long time. Slowly water was added to this since there was a post about the dangers of water and Acetone and Copper coins. Eventually all were removed, allowed to dry, placed on the inside of a kitchen window sill for a long time and still there now.
Not all almost all the contaminations are gone. Although the Indian Head cent
still has the black stuff on it. The Large Cent
and the Indian Cent have both turned an actual RED and are still getting REDER. This is not the so called Cent Red people say, this is really RED. The 1919 Lincoln now is clear of whatever was on it but now really dark. LSQ really came out the best I think. Almost looks like a normal coin. Nickels lost that mirror look too.
Since these were all free, nothing to really loose.
I would suggest just experimenting if you don't mind people saying things like wow did someone claen this coin.