this is a Yugoslav T-54 SO-18 Mod. tank - it's a T-54/55 hull with a Hellcat turret.
Is this vehicle historical? Did it exist? Yes it did.
The story behind it is that Yugoslavia, apart from a number of Hellcats, had a number of T-54's as well and used old T-54 hulls with (fixed) Hellcat turrets to train tank crews. It was never a combat vehicle. Of course, just so we are clear: the WoT model above is a fake. I was asked to put it here by Strv74 from U.S. forums to demonstrate how easy it would be to actually implement an interesting Yugoslav vehicle and that the Yugoslavs built a number of very interesting vehicles that could potentially make a full branch.
Yugoslav vehicles are often forgotten but it's time they received the attention they deserve.