I came across this $1 in my change. To my untrained eye, I don't think it is post mint damage, but I would appreciate input from people with more experience. I hope the pictures are adequate, they are the best I could take with my own equipment.
It is not an error. There is no way this could happen during the striking of the coin. Your coin is suffering from PMD (Post Minting Damage) Either intentionally or unintentionally, the surface has been worn down.