it's a zincoln. Zinc Core. Copper plated there was a gas bubble underneath it. It's gonna start eating itself soon. there's before, during and after pics somewhere ... any cent past 1982 is a problem coin. It's gonna eat itself alive sooner or later .. self-cannibalism.
If you are going to keep it, put it in an air tight coin holder so the rot doesn't get worse and give Lincoln a case of chicken pox.
Very good Claw! Linking Marfan's disease ( mutated BFN-1) to Lincoln Cent, but penicillin isn't a mutagen of the connective tissue fibers. Although zinc rot does look like the mold. Jim