The KV-85 was designed by a design bureau led by Lieutenant-Colonel Kotin.1 He split the bureau into two and each team had different specifications to design for.1 One of the teams was told to improve the KV series as a stopgap for a new heavy tank.1 This design was to become the KV-85.1
The KV-85 was based on the KV-1-S's hull.1,6 The armor was increased to 4.3" / 110 mm.1
Some KV-1Cs / KV-1s6 were upgraded in the winter of 1943-44.
With delays in the IS-85 and the front lines wanting new heavier tanks, an initial 148 KV-85s were manufactured in the autumn of 1943.1 At the start of 1944 all production ceased in favor of the IS series.
The KV-85 had the same 85 mm D-5T gun installed that was to be installed in the IS-85.1 The hull had to be made wider and the 5th crewman was removed to make room for more ammunition.1
KV-85: 102, 1301,2, 1481
It started appearing at the front in the summer of 1943 and was available in large numbers at Kursk in July 1943.
Another source says they didn't first appear until December 1943 against Army Group North.2 The 27th Guard Regiment had 20 tanks in 4 companies and were decimated by the German defenses.2