ISU-152

In 1941 Stalin took a gamble and moved his main T-34 plant in Kharkov to Nizhni Tagil in the Ural Mountains, effectively halting tank development while the new factory was set up and other plants were brought online. The focus on tank development was temporary taken off development and concentrated on making the T-34 quicker and easier to build.
The T-34 obr 1941 (late) is the result of simplifying the construction of the T-34, from the comparatively complex construction of the 1940 and 41 models.     

Like the 1941 model the later version was armed with the F-34 76.2mm gun, and had a welded or cast single hatch turret. It did start to take on a few features that are seen in the later obr 1942 and 85mm models like the armoured hull machine gun cover and the PTK-5 periscope.

T-34 obr 1941, Late Version

KV-1 and infantry attacking in Karelian Isthmus. 1944