The first M4 Sherman production model was designated the M4A1, and possessed a distinctively rounded cast hull. A total of 6,281 M4A1 tanks were produced between February 1942 and December 1943. Armed with a 75mm M3 cannon and powered by a 350hp Continental air-cooled R975-C1 radial gasoline engine, the M4A1 was capable of top speeds of 38.9km/h. Early versions had the M34 gun mount with narrow shield, while the 3-piece gear housing was changed to a 1-piece design in later production runs. Applique armor was often added to the upper hull and turret in order to improve protection. The M4A1 served with many armies on various fronts, including with the British 8th Army in North Africa, where it contributed to the victory at El Alamein.