mystery item in my spare parts box

Does anybody know what these two parts are for? I found them at the bottom of my box of spare parts and they were unlabeled. The box they were in was for all the guns that I shoot more rarely and now I can't remember which gun they go to :confused:

Possible guns: Ruger 10/22, Remington 870, S&W 686, S&W 642, Ruger mkIII 22/45, Beretta AL391, or CZ 527. The screw happens to thread into the other part, but not sure if its supposed to go together.

Attachment 83693
Attachment 83694

Not sure, but I seem to recall a screw like that when I swapped stocks on my 870. But, again, not certain.

also, the screw is about 5/8" long and the other part is 3/8" long

If there were two screws and two holes, it would like a 10/22 barrel V-block.