The Beretta M1951 (M951, 951, "Brigadier", Mod.51) is manufactured by Beretta of Italy as a semi-automatic single action pistol specifically chambered for the 9 mm Parabellum cartridge and designed by Tullio Marengoni (Beretta design engineer).
The Beretta M1951 is of almost solid steel construction (with an experimental Ergal aluminum alloy frame version of approx. 100 produced). The weapon is equipped with an open top slide and a short recoil operated falling block system. The pistol was Beretta's first locked breech pistol on the market, (previous semi-automatic pistols were all blow-backs) and was produced in limited production circa 1953 and in full scale production in 1956 until 1980. The United States commercial version of the firearm was marketed as the Brigadier. After 1968, in the United States, the pistol was briefly referred to as the Beretta 104 in the promotional literature. The 951 was ultimately replaced by Beretta 92 in 1976.
The M1951 was produced and manufactured by Beretta for strictly military use and was then adopted by the Italian navy, army, and law enforcement agencies, Israel, Egypt, Nigeria, and Tunisia armed forces. By license, Egypt (the 'Helwan' produced by Maadi) and Iraq (the 'Tariq') made precise replicas of the Beretta M1951.
A rare variant, the Beretta M952 (starting production in 1963), was chambered for less popular 7.65 mm Parabellum for commercial sales specifically to sport shooters of Italy to comply with restrictions forbidding ownership of the 9x19Parabellum, considering it to be a military caliber pistol. Serial numbers were separately sequenced for this variant, 1001 to 2933. A target version of the Bereta M952 Special was produced from 1971.
A selective fire (machine pistol) version of the pistol, labeled Beretta M1951R (51R and 951A) ("R" for Raffica, burst in Italian) was produced and created ca 1955 and was in very limited production until the full introduction of the Beretta 93R in the 1980s. The Beretta M1951R had a much longer barrel, a significantly heavier slide and could be conveniently loaded with an extended 10 round high power magazine. An optional front grip can also be installed on the weapon.