Given the tank in the picture is a T-34 with a 76mm gun and the primary assault armies would be using T-34/85s i doubt they were the first tanks even though the soviets were using plenty of T-34/76s in 1945.
Crap - went back and read my post again, saw I typed the tank model wrong. Thanks for your further info and correction on that tank. We weren’t allowed as close as the picture shows when I did the slow roll bus drive-by so I never looked, just took the word of the tour guide.