"Photo #3: Commander's hatch with the AA machinegun mount on an ISU-122s SPG (hatch open).
Photo #4: Commander's hatchwith the AA machinegun mount on an ISU-122s SPG (hatch closed).
Even though KV tanks (and not just KV tanks) came with P-40 7.62 mm AA machinegun mounts, it took until October of 1944 for the IS series to get the same luxury, but at least it came with a caliber upgrade.
Aside from the DShK mount, this photo also gives you a good view of the folded up MK-4 periscope used in many Soviet tanks.