Mauser 1912/14: Flapper-Delayed Blowback
Cool Forgotten Weapons merch! http://shop.bbtv.com/collections/forgotten-weapons
Starting in 1909, Mauser had a plan to introduce a family of automatic pistols, with a picket gun in 6.35mm (.25 ACP) and a military/police service pistol in 9mm Parabellum that shared the same basic look. The initial 1909 prototype in 9mm was simple blowback, and proved to be a failure. The next attempt was a simple blowback 6.35mm, which was quite successful, and was marketed as the Mauser 1910, as well as the 1914 in .32 ACP (7.65mm). With that selling well, the company went back to its 9mm gun, and began experimenting with locking systems. After failing to get a vertically tipping locking block to work, they came to a flapper-delayed blowback system that was expensive, but worked well. That was the Model 1912, in 9x19mm.
Between 1912 and 1914 about 200 examples of this gun were made, with production standardizing by about serial number 50. Later examples were made for a military market, with 500-meter tangent sights and detachable holster stocks. Any hopes of challenging the Luger in Germany military service were dashed by the death of Paul Mauser in May 1914, coupled with the outbreak of war in August. The project fizzled to an end, and was never restarted after the war - although elements would go with Josef Nickl to Czechoslovakia and eventually show up in the CZ Model 27...
For more information on this and other Mauser handgun developments, I recommend "Mauser Pistolen" by Schmidt, Speed, and Weaver:
6281 N. Oracle 36270
Tucson, AZ 85740