in Europe and Colt Firearms in the United States. Since Colt did not want to produce it, Browning chose to patent and produce this design in Europe only. Introduced in 1910, this pistol used a novel operating spring location surrounding the barrel. This location became the standard in such future weapons as the Walther PP and Russian Makarov. The Model 1910 incorporated the standard Browning striker-firing mechanism and a grip safety along with a magazine safety and an external safety lever (known as the "triple safety") in a compact package. It was offered in both .32 ACP (8-shot) and .380 ACP (7-shot) calibers and it remained in production until 1983. It is possible to switch calibres by changing only the barrel. Also noteworthy for European pocket pistols are the Mauser Model 1910 and Mauser Model 1914, chambered for .25 ACP and .32 ACP respectively, both of blowback and hammerless design, which were very popular as civilian small handguns. The .32ACP version was considered powerful enough for the Kriegsmarine as well as security forces of the Third Reich, and reworked as the Mauser Model 1934, with only minor modifications. The Mauser HSC, produced during the war in .32 ACP for the Navy and later police and army units saw substantial production and sales after the war (upgraded to .380 ACP), and was successfully introduced to the US market. The Colt Detective Special is a carbon steel framed double-action, snubnosed, 6-shot revolver. As the name "Detective Special" suggests, this model revolver was used as a concealed weapon by plainclothes police detectives. It was made with either a 2-inch or 3-inch barrel. Introduced in 1927, the Detective Special was the first snubnosed revolver produced with a modern swing-out frame. It was designed from the outset to be chambered for higher-powered cartridges such as the .38 Special, considered to be a powerful caliber for a concealable pocket revolver of the day. The Walther PP (Polizeipistole, or police pistol) series pistols were introduced in 1929 and are among the world's first successful double-action, blowback-operated semi-automatic pistols, developed by the German arms manufacturer Carl Walther GmbH Sportwaffen. They feature exposed hammers, a traditional double-action trigger mechanism, and a fixed barrel that also acts as the guide rod for the recoil spring. It was offered in both .32 ACP (9-shot) and .380 ACP (8-shot) calibers. The Walther PP and smaller PPK models were both popular with European