Even with one side incused and the other in relief in the exact same spot on opposite sides? Just curious here.
When I looked at this I noticed that the copper looking piece on the reverse looks exactly the same in reverse on the obverse if that makes sense. Well not exactly but pretty close.
At this stage I say it is too far gone to make a call as to what caused the areas to look as they do. Besides the cool factor....value in my opinion would be melt....even if a strike thru
Didn't think of that but an arc weld contact would create splatter and much more damage but possibly a wire feed Arc could explain some of it.