Comet was essentially a British Pershing in terms of armour protection, limited runs included the Tortoise (as numerous as ostwinds ever were), etc. etc.
Actually, not quite... Comet was tougher than cromwell, but nowhere as tough as the Pershing... For what im looking at. It actually had a gun mantlet, and a pretty tough one compared to the lack of one for the cromwell, but that matters little in this game.
I have never heard of the tortoise in combat, nor do i ever want to see it. I just assume the Ostwind represents the many odds and ends of vehicles the germans put flak cannons on.