Captured equipment

Notice this machine has a German style commander's cupola indicating it was captured by Soviets - converted to this type - recaptured by Germans - and re-recaptured by Soviets.

The Red Army’s Panzer III 76mm SPG
The SU-76i was built or re-built by the Soviets because, while speeding up their huge production of tanks, they still faced shortages in certain areas. Furthermore, the original SU-76 model had several flaws. They were unreliable and not a pleasure to drive, so much so the Soviet tankers named it “the Bitch”. During the fall of Stalingrad, the Soviets had captured several StuG and Panzer III tank chassis in relatively good condition. With the thought of rearming them with bigger Soviet guns, they were shipped back to factory 37 at Sverdlovsk.

This image: SU-76i Command Vehicle with Panzer III cupola fitted to the roof
http://www.tanks-encyclopedia.com/ww2/soviet/soviet-su-76i.php