This Abraded Patch on Washington Dollar Intrigues Expert

Well-known die variety expert Billy Crawford sent me these enigmatic photos. There is a patch of surface area in the field of this Washington Presidential Dollar reverse that has been abraded by a Mint technician. Mint workers abrade the coin dies when they need to clean up problems such as clash marks or other damage to the face of the dies. After the abrading, which obscures the fault, the die should be polished to bring the surface back to a smooth texture. The first photo shows a wide angle view of the area we are examining here.