You have a commercial firearm built for civilian use that was purchased by the goverment under a blanket pacurement, then stamped with US property marks. Early war production. We were so short of guns when the war started the military actually went to hardware stores to buy needed guns the stories go. The fact it has an engraved reciever, high gloss bluing, and checkered stock bear this out. The FJA intials are the inspecters marks and the crossed cannons are military as well. Nice factory riot barrel, many were full choked long barrels that were cut down.