I believe pre=WWII French shotguns had to be given-up to the Germans, in which case they were shipped back to Germany, or they were buried or concealed. A lot of them came out pitted. I have a legitimate war-trophy Saint-Etienne boxlock, however, which is still in pretty pristine condition...somehow. Heaven knows where it was looted from.
https://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=481696And Ted, coming back from Vietnam you couldn't believe the candy-@$$ inspections we went through with the MP's seizing all sorts of stuff....they tried to take my Randall Knife Model 14 because I sharpened a bit of the top edge (no double-edged knives allowed). They confiscated a Montagnard cast iron spear..... crazy stuff but the military does that.
In Afghanistan about 2009 some general up at Bagram decided that if you wanted to send a breech loading, center-fire rifle back, it had to have ATF approval...this included 1866 Snider-infields, and 1871 Martini-Henry's. Of course most of those were Pashtun copies but ATF in Martinsburg WVa told me they couldn't tell the difference so just gave the approval (copies are not allowed in). ATF was pretty upset about the paperwork deluge...because anything earlier than 1898 is not a firearm in the USA. But that's what you get when an underemployed general decided to frick with the troops.