Valentin Hafner
HAFNER (HAeFNER) Valentin, Kassel, Hessen/Germany, born 1847 (father: gunmaker Wilhelm Haefner), died after 1921. Valentin Haefner received his title for making (supplying) guns to the Royal Court of Hessen. The German monarchy was abolished in 1918 after the Great War. Either this gun was made before that or the German gunmakers by royal appointment did not care much about the Weimar republic.
Guns, any info about your gun or pics would be appreciated!!
Thanks to Jani of Montenegro for providing these details and insights on V Hafner a while back, and my 30" barreled 16 ga Hafner: