I know it was damage... I was looking more for the type or cause. Moreover, I'm not sold on the "post" statement. I think something failed here i.e, die/planchet. The product is ovaled toward damage. just curious.
We would never know the cause of post mint damage unless we were there when the damage happened. As for a mint error, this type of damage isn't something seen/caused during the minting process, thus the post mint label.