A friend of mine has an Eduard Kettner double barrel with the 118/35 proof mark for bore diameter also. This mark is found on many pre 1912 9.3x72Rs (and other case length 9.3s), but his is chambered for 9x58 1/2R S&S ( his was made by S&S for marketing by Kettner). Your rifle was actually made before 1912, as evidenced by the 118/35 marking, but re-proofed later, hence the 1954 and 58 dates. I have a prewar drilling that was re-proofed after the war, and like yours the new proofs are in a very small font. I am unable to see your new proofs well enough to tell why( or for what) yours was re-proofed for. If you look around in the website Skeetx linked, maybe you can figure it out. Look for the post war West German (FRG) proof marks and pay particular attention to the initials inside the Bundesadlers. They are the key to the meaning of those particular marks. Your friend is lucky.
Mike
