I'm still pretty sure that Westwood designated the Light Tank "M2-F" when Tiberian Dawn was first released. The M2A2 doesn't have a 75mm cannon.
Cowmisfit, maybe you're thinking about the Soviet IS-3 heavy tank. The Israelis captured some of them from the Egyptians and used them in their own armed forces during the 70's. The Apocalypse Tank from Red Alert 2 is very similar to the IS-3.