The following information on early Mauser revolvers and pistols comes from Chapter 39 of Mauser Rifles and Pistols by W. H. B. Smith. Mauser Rifles and Pistols is also available to purchase in print.
Mauser made two patterns of revolvers, both of unusual design utilizing a coil mainspring as shown in the drawing housed below the cylinder in the frame.
Model 77 Mauser Single Shot Pistol (1) Right side view, action closed. (2) Right side view with action open and cartridge inserted in chamber. Note that the act of opening the pistol to load drives back the concealed hammer and cocks the mainspring. (Click to Enlarge)
Model 77 Mauser Single Shot Pistol Pistol loaded and ready to fire. Note the short hammer travel. Pistol fired, all parts at rest. (Click to Enlarge)
The first type was a solid frame revolver. A loading port of standard type was provided on the right side of the frame. This was a standard single action type weapon in which the hammer had to be cocked for each shot.
Model 86. Mauser Magazine Pistol With Tube Magazine And Block Lock Top Line: Details of lockwork, all parts at rest, left side view. Second Line: Details of safety and lock plate. (Click to Enlarge)
Model 86. Mauser Magazine Pistol With Tube Magazine And Block Lock Top Line: Left side and rear details. Magazine is empty, but hammer is at full cock and pistol is locked. Second Line: Left side view of Carbine model of this pistol design. (Click to Enlarge)
The second type was a hinged frame design with automatic extraction. This also was a single action revolver. The act of cocking the hammer caused a ball shape protuberance at the lower end of the hammer to thrust forward a guide and compress the mainspring.
Model 78 Mauser Revolvers Left and right views of Mauser solid frame revolver. This single action revolver was loaded through a standard type ejection port on the right side of the arm. Note the unusual mainspring and cylinder turning design. (Click to Enlarge)
Model 78 Mauser Revolvers Left and right views of Mauser hinged frame revolver. Turning forward lock (V) permitted the barrel and its strap to be hinged up for loading and for extraction. The firing and cylinder revolving systems are those of the solid frame type. This too was a single action arm in which the hammer had to be thumb cocked for each shot. (Click to Enlarge)
The really unusual feature of this design, however, was the method of revolving the cylinder. This was effected by a zig-zag series of cuts in the cylinder wall. During the act of cocking, the stud operating in the cut brought the cylinder around the distance of one chamber and lined the chamber up with the mouth of the barrel.
Model 78. Mauser Improved Revolver Top Line: Left side and rear cutaway views showing details of construction. Second Line: Detail• of hammer, mainspring and cylinder revolving mechanism. (Click to Enlarge)
Model 78. Mauser Improved Revolver Top Line: Side and rear elevations. Second Line: Side, rear and front cylinder views. (Click to Enlarge)
Samuel Colt developed a cylinder revolving on this general system. It was never produced in quantity, however. The English Webley-Fosbey Automatic Revolver and the U.S. Union Arms Company Automatic Revolver also used modifications of this cylinder system.