It looks more like something was stuck to the reverse, like soldered. It's too straight-looking for me to think it is something else. I could be wrong though.
It may be a split die in progress (die breaking in half). If so, it's not junk. Don't ask me how much it's worth; I don't know.
The black spots around it was from the acid flux used with the solder. Most likely a pin or clip to use as buttons on a large coat
