The Komsomolets was used by the Soviets, the Germans and Finland (captured vehicles). The Soviets and the Germans used a very similar looking AT gun: 37 mm Pak 36 (German) and 45 mm M1937 (Soviet) which was also used by Finnish forces. The main difference between the guns was the breech, which is hidden by one of the soldiers. The Finnish smg means propably, that it's the 45 mm gun.