n the British naming system the major variants were identified by Mark numbers, the M4 being "Sherman I", the M4A1 "Sherman II" and so on. Letters after the mark number denoted modifications to the base model: "A" for the 76 mm L/55 gun instead of the 75mm, "B" for the 105 mm M4 L/22.5 howitzer, "C" for the (British) QF 17 pounder (76.2 mm) gun, and "Y" for the wider tracked HVSS type suspension.