Franz Kettner had shops in both Köln (Cologne) 1850 and Suhl circa 1910 until WWII.
Eduard Kettner of Köln (Cologne) established in 1865 with a factory in Suhl, I’m not sure when they stopped making guns. This company was in business a few years ago with retail stores in more than one German city. Not sure of the relationship between the two but both are listed in the early years as gunmakers.
I can see the one picture just fine,(nice looking gun) take off the barrels and take a photos of all the proof-marks on the barrels and the action please.