I would suggest you get as many good detailed pictures of all the details you have listed, and repost them in the German Gun section of this BBS- We have many members who can assist you further, and their knowledge is encyclopedic in this area of expertise. Is this a outside hammer gun, or a hammerless? In my somewhat limited experience with these well-made shotguns, the 16/1 marking is common, and unless stamped 70mm ( 2.75") chambering, most of these have the shorter 65mm chambers. So even with the fine Krupp steel barrels, you might want to shoot the current 2.5" light loads in 16 gauge, such as RST sells.