The polished are\a appears to be recessed into the coin. I don't know what would cause damage like that. It looks for all the world like tooling, though the coin doesn't seem to be badly worn enough to need tooling.
Perhaps someone tried to polish it with a power tool like a dentist's drill, and gave up halfway? Maybe they were aiming for some kind of frosted-proof effect?
Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis