1. Initial production, low-bustle 75mm turret
That's the basic type which appeared on early and mid production M4, M4A1, M4A2, M4A3 and M4A4 75mm gun tanks. It had the low radio bustle at the rear, a shell ejection port (a.k.a. pistol port) on the rear left side, and had only one hatch. Most were built with the early split commander's hatch with straight hinges. This is also the type of turret that received the welded-on appliqué as a means to compensate for the thinning of the right front cheek to make space for the new gun controls. This type of turret initially received the earlier M34 gun mount with narrow shield, later replaced on the production line with the revised M34A1 gun mount with full-width shield.

2. Late production low-bustle 75mm turret:
Same as the previous, but most of these were built without the shell ejection (pistol) port, and all had the reinforced (thickened) right front cheek and a single hatch. These all had the later M34A1 gun mount, and the early split commander's hatch with straight hinges. This type of turret was also seen on most 75mm Sherman types, though less commonly, and on initial production M4 with composite hulls.

3. High bustle 75mm turret:
This is the final type. It had the rear buslte raised to make better clearance for the new large hatches on revised Sherman hulls, a shell ejection (pistol) port, and the cast-in armor supplement on the right front cheek, as well as an additional, oval-shaped hatch for the loader. These were built with the M34A1 full-width gun mount. This turret, with a second roof ventilator added, was also used on 105mm howitzer (assault gun) tanks. High bustle turret were initially built with the late split commader's hatch with spring-loaded hinges, and later with the new all-round vision, single hatch cupola. This typer of turret was used on most large-hatch M4 (105mm only), M4A3 (both 75mm and 105mm) and M4A2 (late 75mm) tanks, and on late production composite hull M4.