85mm obr 1939 gun (x2, Late) (SU543) M-1939 (KS-12) 85mm Anti-Aircraft Gun The 85mm obr 1939 anti-aircraft gun (KS-12) was developed by M. N. Loginov at Artillery Plant No. 8 at Kaliningrad (later relocated to Sverdlovsk) as a replacement for the 76mm anti-aircraft gun.