A circled 16 denotes proof for 2 1/2 inch chambers. That age of gun they were all 2 1/2 in. chambers. 2 3/4 chambers in German shotguns were very, very, very uncommon until after the war. Unless you know they've been opened up or you've measured them or had them measured, you have to assume they're 2 1/2 chambers. You can shoot 2 3/4 shells in 2 1/2 in. chambers but opinions are divided on the subject.
Until quite a while after the war, German proofs NEVER denoted how much choke. A crown over a "W" denoted a choked bore but NEVER the amount of choke. I have no idea what the F might stand for unless someone stamped it on there later. It's entirely possible there is no name of any kind on the gun. There is A PILE of unmarked German firearms out there, I have a few. I mean, well, you thought the maker was Erhardt Lauf…….if that's the case, ol' "Lauf" made the majority of German guns as his name is stamped on an awful lot of them. Is it Rhenmetall or Rheinmetall? A lion on the side....side of what, the receiver?
If you can take the time to take different pictures of different views of the gun and all the proof marks on the bottom of the barrels and on the water table, I might be able to help you.
