Actually it is not the S-65 Stalinets. It is the СТЗ-3 ( STZ-3 ). The enlarged pics with the factory logo is a little bit blurry but the first letter there doesn't look like X or C. I would say it's the A what means that's the tug was made by the Altaic Tractor Zavod after evacuation of the Kharkiv Tractor Zavod there.