You are right it is CUD, I apologized, the pictures are not clear enough, I checked it under a magnifier and I can see, the "lumps" per say, CUDS, many of the them small and a couple of large ones, the other side of the coin has quite a few also. I'll try to get better pictures. thanks you.
It suffers from zinc rot. The plating broke and let the environment get to the zinc core. No, it's not a cud.
