You have me on that one. Can't tell much from the pictures but it looks to be common corrosion. It may look different in hand though.
At first, I thought you had discovered a new planet in our solar system, but then I saw a photo of the obverse. I'm guessing that it is either chemical or environmental damage. Chris
Um........uh.........er.........let me think about this for a bit.........well...........you see...........nooooooooooooooooooooooooooooooooo! Chris