isn't it nearly impossible to tell the Crusader III AA MkII/III, the Centaur AA MkII, and the Cromwell AA MkII apart from the front? their chasis all look similar and they all have the same turret with twin 20mm Oerlikon/Polsten guns.
It's a Crusader AA tank. You can tell by the raised driver's cowl. A Centaur lacks the cowl and instead the driving compartment is on the same level as the hull top, plus it's straight on the front and has two crew positions.
For comparison: