how much does it weigh? I looks like it could be an eliptical clip that got widened/misformed due to the eregular shape in the upset mill and then was squeezed into the coining chamber when struck. I think thats why finning happens even on normal sized planchets because they either dont fall into the press and have a bit of one edge resting on the collar then when the die come down it presses it into the chamber dragging some metal down the collar then the striking die smashes it back down to form the rim. I forget the other explanations buts thats one way I see it could happen. some are rasied and looks like those push the die out of alignment cause they get pinched inbetween the die and the collar. Some even can have a strike clip where a small part of the coin is clipped or pinched off because it didnt fall into the coining chamber and was resting on the collar but thats a different error all together. check the weight compared side by side on other cents as control weights.