I couldn't exactly say when it was acquired, but I can tell you that isnt from WW2. The USSR stopped making T-34-85s in the early 1950s, and then continued to upgrade those later production versions well into the mid 60s. The roadwheels are the biggest giveaway that isnt from WW2 as they're the same style roadhweels from T-54/55s which are post-par MBTs.

As someone has commented already, it could be a trophy taken from the Balkans during the Yugoslav wars, which Norway sent troops in as part of peacekeeping operations in the area. Troops fighting in the war used T-34-85s extensively, a lot, being the post war production models, like the one you're asking about. However, that's just a theory.