From the article:
The initial KV mounted both a 76.2mm and a 45mm gun in the turret with single machine gun in the hull. With the outbreak of the Winter War the KV was sent to the front, but only after the 45mm was replaced with a 7.62mm machine-gun, while another machine-gun was mounted in the rear of the turret to protect the tank from infantry assaults.
Towards the end of 1940 the 76.2mm L-11 tank gun was replaced with the new 7.62mm F-32 gun, this became the KV-1 obr 1940. In the spring of 1941, in response to intelligence on the Germans a decision was made to increase the armour of KV-1. Additional armour plates were bolted to the hull and turret. This modified KV became the KV-1e ("e" means "ekranirovaniy" or "with shields"). At the start of the German invasion the Red Army had 639 KV-1 tanks.