I'd settle for a DNA sample. Hair, scat, bones, teeth, spit on a chewed up branch. On the other hand, No.4 parts, either loose or assmbled into a working projectile launcher aren't too hard to find. Given that you have 4 million chances in just WWII production alone, there's gotta be some hope a few weren't rendered down higgledy pigledy and put back together as Frankenrifles.