When I was a teenage dishwasher, we used to occasionally throw a nickel in the industrial garbage disposal and run it for a half hour because, I don’t know, teenagers do weird stuff like that. Anyway, it would mushroom the edge and give it an appearance much like that, except that the diameter would be reduced. It probably didn’t do wonders for the Hobart either.
If Mike Byers says it’s Post-strike damage then I’m sure that must be solid info.