I was putting together a cheap AR15 lower last night and this is what was included in the LPK for the rear take-down pin. It's obviously not that, so, what is it? It's about the same length as the front take-down pin.
I got my apple 12SE out and took a photo of the thing and activated the find-em application.
It took 15 min but it found out what it was.
It is the main actuating joint bolt for the tin woodman's left knee, AND HE WANTS IT BACK!!!