The Japanese aspect on the rifle is very possible as there is a large Japanese sub culture out here in my part of South Jersey. The area was very popular during the war for refugee camps. Caliber I have no clue on. Would it be advisable to take a wire brush to it in different area's to look for markings or to just leave them as is, and what all areas would be good to check. Again thank you very much for all your help with these weapons.