The T-34 medium tank is one of the most-produced and longest-lived tanks of all time.

Identification of T-34
variants can be complicated. Turret castings, superficial details, and
equipment differed between factories; new features were added in the
middle of production runs, or retrofitted to older tanks; damaged tanks
were rebuilt, sometimes with the addition of newer-model equipment and
even new turrets. Some tanks had appliqué armor made of scrap steel of varying thickness welded onto the hull and turret; these tanks are called s ekranami ("with screens"), although this was never an official designation for any T-34 variant. 

OT-34 - A T-34 flame-thrower tank fitted with an internally mounted flamethrower replacing the hull machine-gun. Usually it was a modified Model 1941 with the ATO-41 flamethrower or Model 1942 with ATO-42.