2016 D Mint Lincoln Penny.

Well in the first close-up of the reverse the rim is gone. I think the rim along the copper plating and some of the under-lying zinc was carved away somehow. Notice how the copper plating is at an angle towards the edge. same thing at the opposite end of the reverse as well.

Agree with zinc rot

Yes looks like PMD. As Dearborn mentioned, something scraping away the copper on the coin which causes the zinc core to be exposed normally, such as spending time in a street. This one looks like the zinc core underneath even took a hit. Its quite darkened from wear so its clearly had its share of environmental exposure. Normally at that point you will start to see white zinc bloom or Hydrozincite (zinc carbonate) form to protect the exposed zinc core.if the zinc is exposed which has a silvery type look https://www.error-ref.com/incomplete_plating/ Should the zinc core stay exposed and the zinc bloom or Hydrozincite (zinc carbonate) can't remain on the exposed zinc for some reason and not being able to stay put to protect the exposed zinc, more of the coin then gets sacrificed eating away the zinc aka zinc rot. If nothing knocks off the zinc carbonate protective layer it can take forever to rot. https://www.error-ref.com/zinc-dete...ncoln-cents/

I liked the two threads, Thad! The breakdown and scientific reason and the nutshell.