I have no definite answer, but my first guess is that this looks like a laminar failure, a piece flaking off, most probably after the coin has left the Mint.
This sort of thing can happen if there are problems rolling the strip prior to blanking, and shows up with a failure such as this during circulation.
This sort of thing can happen if there are problems rolling the strip prior to blanking, and shows up with a failure such as this during circulation.




















