At first sight, it's a simple model 1942 T-34 turret used as a bunker. However, looking at the barrel length, it's far too short. This isn't a simple T-34, it's using the F-32 gun from early KV-1 tanks! However, the F-32 gun that was meant for a heavy tank didn't fit into a medium tank's smaller turret that easily. It's clear that whoever made this emplacement had to do some work adjusting the turret "cheeks". Instead of being the common quarter-spherical shape, the side is now a 90 degree angle, forming a cylinder.