The first series production batch of KV-1 tank's, sometimes called the KV-1 Model 1939, had the L-11 76 mm gun in a low-slung gun mantlet.
This weapon, developed by the SKB-4 at the LKZ Kirovskiy Plant, did not meet with official approval, and was quickly replaced by the F-32 gun designed by the Grabin artillery design bureau.
The early Model 1939 series-production batch still fielded the pistol port in the front of the driver's compartment, while the late production batch of Model 1939 already used the ball-mount for the 7.62mm DT machine gun mounted in the bow. This addition became standard later.
Early models had a simplified rear-turret machine gun. later the standardised ball-mount was installed here.
In total, some 141 KV-1 Model 1939 were manufactures at LKZ.