I can't find anything on this si I thought I'd ask the experts. I'll try for better pics later if I can.
I may be wrong, but I've been told that acetone has a tendency to turn copper cents a pinkish color. I'm not really sure if it is glue. It could be some other form of chemical or environmental damage. Maybe you could try soaking it in virgin olive oil, first. Chris
Have you tried water yet? They appear to be a thin film of copper acetate crystals, maybe from someone used a vinegar solution and allowed it to dehydrate.. Hard to tell from photos.
Not an error, post mint chemical exposure. Not worth trying to conserve. Other than distilled water, the cost of the solvent will exceed the value of the coin.