I don't think there's any magic here. This one was probably wrapped in a newspaper from the stack at the time and not touched since. It was undoubtedly put away for nefarious reasons and never retrieved, so here it sits. The damage to the stock does look like a grenade sight mount screws but hard to tell from here. There were probably no more parts when it was stored than there are now, they may have been pilfered in the first place to make other stuff run. This just fell by the wayside. I guess the stock could be resurrected, but the rest needs a bead blast and park. The barrel needs a sh*tcanning...