Judging by the length of the barrel it's a civilian Winchester Model 12 "Heavy Duck" shotgun which had a 32 inch barrel in the mistaken belief back in the '30's, '40's. and '50's that long barreled shotguns 'hit harder' than short barreled shotguns. The shotgun was designed to put a lot of shot into a bird at long distance and worked best with heavier loads. I had one back in the '70's but much preferred the dual action bars on my 870.