Looks like the rim got a hit. PMD also wear on the coin. Coins get used for currency. You'll find them in cash register drawers bouncing all around and getting hit by other coins. they get dropped, driven over in parking lots, used as a buffering in hammering (I do that, lol); stored up by the tonnage in purses, shipped by Loomis and other money transport companies in large heavy bags, etc. They are handled roughly over time.
