A Sauer & Sohn, Suhl, hammer drilling Model XX. Made about 1890 according to serial number and lack of official German proofmarks. The “wild man” was a S&S trademark, while that eagle and the crowns were their private quality marks.
It is of common German hammer drilling design. The “Serpent” side lever is the action opening lever. The small top lever is the barrel selector. Pushing it over to the left moves a transfer bar in between the breast of the right hammer and the firing pin of the rifle barrel, barely visible in the 6th photo. At the same time that transfer bar blocks the hammer nose from hitting the right shot barrel firing pin.