I've come into possession of a WWII Paratrooper gravity knife and was wondering if there is some way to find date of manufacture or number made. It has a crowned man (King?) holding a sword sitting on "SMF". The opening lever has a 1 on it and 385 under it. My father-in-law had it and he's passed away and my mothr-in-law gave it to me. Any information would be appreciated. Thanks