It was a mock-up turret on the chassis of T-34. It was very convincing. Operational Tiger I's are extremely rare. That is why you never see "the real deal" in movies.
One thing that gave it away was when Capt. Miller takes his submachine gun a sprays the inside of the vehicle through the driver's viewport (rectangle opening on the front of the tank). A real Tiger had 6 layers of armored glass there making the Captian's actions impossible.
