Developed in 1937 at Armored Vehicle Repair Base No. 12 (Kharkov command). The BT-SV used parts and components of the BT-7. The hull used 10â??12-mm structural steel plates that formed sloped armor; the mass-produced vehicle was supposed to feature 25-mm homogeneous armor steel plates. The vehicle passed trials but did not see service. Subsequently, its sloped armor design was used for the A-20 experimental tank and T-34.