In the aftermath of World War One, German police forces were responsible for maintaining social order is a very chaotic Germany. They were reequipped with small arms, and in particular needed pistols. The ideal sidearm would have been the P08 Luger, but the Treaty of Versailles caused Luger production at DWM and Erfurt to be shut down, and the Lugers allowed to remain in government possession were allocated to the Army. The police looked about for a suitable alternative, and found the Prussian “Red 9” C96 Mauser pistols.
The C96 was really more of a martial handgun than a police handgun, and the police proceeded to make a couple changes to bring the guns more in line with the police role. The barrels were cut down from 5.5 inches to 4 inches, and the 500m adjustable sights replaced with fixed notch sights. It is unclear exactly who made these alterations, but it was probably the Erfurt arsenal. The guns then saw active police use (generally without their shoulder stocks) into the 1930s, when German rearmament included expanded Luger production. At that point, some were recycled into Wehrmacht use, to see use in World War Two.
This particular example has two police markings. On is. “St. 140.”, which is of unknown meaning. The other is “S. G. V. 39.” which indicates the 39th item of the 5th command of the Gumbinnen Schutzpolizei. It was taken as a souvenir by an American soldier in April 1945, who mentioned it in a letter to his family at that time. Gumbinnen was in East Prussia at the time, and is now part of Poland.