The Mann pistol was a German pocket pistol produced by Fritz Mann Werkzeugfrabrik.
This pistol was designed by Fritz Mann, who established the a Suhl-based company to produce the weapon in 1919. Production began in 1920, but a lack of sales saw it discontinued just four years later. A .32 caliber version was proposed but never made, due to safety concerns. Mann then produced a more conventional pocket pistol in .32 and .380 caliber. The company went bankrupt in 1929.
The original Mann was a blowback-operated pistol. The entire frame was a solid piece with no slide. Running across the top of the barrel was a recoil spring, which was attached to the bolt via a small connecting rod. The external cocking piece in the rear of the weapon was linked to both the connecting rod and the bolt itself. The barrel protruded out at the front and could be pulled out of the frame by twisting the muzzle.
The Mann did not have a breech locking mechanism, so the gun's operation had to slow down enough to eject the cartridge. It had a circular chamber groove, which slowed the cycling down enough, where pressure in the barrel forces the cartridge into the groove, delaying the action.
The gun could only handle low-velocity bullets, despite unsuccessful attempts by the designer to produce versions in larger calibers.
Of note is that the pistol is known to bulge cases when firing; this was apparently intentional.