This one is a bit strange, I would assume some kind of environmental damage. The surface looks like it's flaking off, but it also kind of looks like a nice warpaint job! As clueless as I am on it, I like it!
Heh-heh, I bought this one just to prove with a coin in hand that the newly PCGS designated unique "1942 high relief pattern" cent had the same "worms" along the forehead as tons of regular 1942 circulation coins, so it probably wasn't some special new high relief hub. Then I got banned.