After making their big break with the adoption of the Model 1871 Mauser rifle by the newly unified German government, the Mauser brothers, took a shot at getting the handgun contract for the military as well, with this revolver, the Model 1878. It is often colloquially called the Mauser Zig-Zag because of its conspicuously grooved cylinder, although of course that was never an official designation.
The guns were made in the official 10.6mm German Ordnance cartridge, as well as 9mm and 7.6mm cartridges for the civilian commercial market, with a couple different frame sizes. Unfortunately for Mauser, the guns proved too complicated for military acceptance, and they did not sell very well on the commercial market either. The external cylinder rotating tracks required special accommodation, as the cylinder had to have a chamber precisely in line with the barrel to latch closed after reloading. This was done by adding a manual locking lever at the front of the cylinder, which doubled as a safety catch.
Of course, what made the guns unsuitable for the military does make them pretty unusual and interesting for collectors today...