Introduced in 1935 and based on the French "Brandt" mortar, the M1 was a primary indirect-fire infantry weapon through World War II and into the 1950s. The M1 operates on similar principles to the WWI Stokes Mortar, where rounds are muzzle loaded and allowed to drop on a fixed firing pin, a setup that is extremely robust, highly effective, and permits an impressive rate of fire. The main tube and endcap are finished in green, with the endcap bearing the maker's marks and serial number. The baseplate and bipod are also finished in green, with the bipod bearing a brass E.B. Co. data plate on the windage adjustment mechanism and fitted with an M4 sight.