What would be the most proper designation for this tank?

I get that it's a sort of silly question, but what would be the most proper designation for the ankou team panzer IV at the end of the series? It's usually referred to as a panzer IV ausf. H, because that's the standard it was upgraded to, but I've also seen other things like panzer IV ausf. D mod H, or similar names, so I'm curious what such a vehicle would be referred to officially if it were real, and whether or not such an upgrade was (or could have been) done irl.