Agree, post-strike damage. May have been intentionally 'sanded down', or may have suffered from intense lateral abrasion in an 'industrial' setting, like being face down on a smooth concrete shop floor, trapped under a heavy object, and slid around for a time as the heavy object was occasionally moved. In either instance, the coin appears to have served in circulation for many, many years after the abrasion/sanding event. Cool find.