First, my apologies for the first images I posted. It was later in the day and the light was low. The images attached are from this morning and give you a better view of the date. By the way, I never saw the string until better lighting.
Can you provide a better pic of the reverse and also a good closeup of the FG on the reverse???? I am tending to think this is 1974-82 coin and some years were known for having really unpretty reverses, even as minted.
First, I'm not sure what it is but I'm leaning towards some type of lamination error. The reason is for that is the way the piece chipped off the planchet. Copper is a very malleable metal, and I would expect if it was a PMD hit or gouge you would see metal smearing and I don't see any of that. So IMO, a lamination fits best It could be from an occluded gas bubble or maybe an alloying or contamination issue (but I don't see any color differences that would indicate that. Just my thoughts to see if it stirs up any other ideas.
Photos aren't the clearest, but it looks like a lamination to me. And please don't send it to PCGS or NGC or ANACS. It's not worth the fees whatsoever.