The Walther PP (, or police pistol) series pistols are blowback-operated semi-automatic pistols, developed by the German arms manufacturer Carl Walther GmbH Sportwaffen. It features an exposed hammer, a traditional double-action trigger mechanism, a single-column magazine, and a fixed barrel that also acts as the guide rod for the recoil spring. The series includes the Walther PP, PPK, PPK/S, and PPK/E models. The Walther TPH pocket pistol is a smaller calibre pistol introduced in 1971 identical in handling and operation to the PPK. Various PP series are manufactured in Germany, France and the United States. In the past, the PPK version was manufactured by Walther in its own factory in Germany, as well as under licenses by Manurhin in France; Interarms in Virginia and by Smith & Wesson in Maine. Since 2018, PPK and PPK/S models have been built at the factory of US-based subsidiary Walther Arms, Inc. The PP and the PPK were among the world's first successful double action semi-automatic pistols. They are still manufactured by Walther and have been widely copied. The design inspired other pistols, among them the Soviet Makarov, the Hungarian FEG PA-63, the Polish P-64, the American Accu-Tek AT-380 II, and the Argentinian Bersa Thunder 380. The PP and PPK were both popular with European police and civilians for being reliable and concealable. During World War II, they were issued to the German military (officers), including the Luftwaffe, as well as the uniformed Ordnungspolizei and plainclothes detectives of the Kriminalpolizei. PP Series The original PP was released in 1929. It was designed for police use and was used by police forces in Europe in the 1930s and later. The semi-automatic pistol operated using a simple blowback action. The PP was designed with several safety features, some of them innovative, including an automatic hammer block, a combination safety/decocker and a loaded chamber indicator. All members of the PP series share a common takedown procedure. The trigger guard is hinged; by pulling the trigger guard downwards, the slide can be drawn backwards past the normal stopping point, lifted clear of the slide rail, and then guided back forward to clear the barrel. With the slide removed the blowback spring around the barrel is free and can be removed as well. Variants PPK The most common variant is the Walther PPK, a smaller version of the PP with a shorter grip, barrel and frame, and reduced magazine