Howdy I ended up with two of these:
I think it may be for a 22 pistol, but not for sure. It sure looks like it's for a 22 by diameter of the hole. Also it's made from a light metal, maybe aluminium. In the same box were grips for Ruger Mark II's and some High Standard 22 items. I don't think it would fit on either one though.
Thanks in advance!