The Thompson (often referred to as Thompson submachine gun) is an American submachine gun, invented by John T. Thompson in 1919, that became infamous during the Prohibition era. It was a common sight in the media of the time, being used by both law enforcement officers and criminals. The Thompson was also known informally as: the "Tommy Gun", "Trench Broom", "Trench Sweeper", "Chicago Typewriter", "Chicago Piano", "Chicago Style", "Chicago Organ Grinder", and "The Chopper".
The Thompson was favored by soldiers, criminals, police and civilians alike for its ergonomics, compactness, large .45 ACPcartridge, reliability, and high volume of automatic fire. It has since gained popularity among civilian collectors for its historical significance. The M1928A1 is a rare gem recovered by gun collectors and a few of Magnum's evidence lockers. The actuator has been modified to increase the rate of fire.