A VERY SERIOUS CONCERN

[Seekerdolls]

[EXTREME AUTHENTICITY INTENSIFIES]

[kvasius]

Yes, somebody claimed the mount was post-war, but both gun and mount are pictured on IS-2 in Danzig in early 1945.
The issue seems more to be that this very IS-2 mount might not have been retrofitted on T-34/85 before the late 50's or early 60's.

I claimed it in Discord. I did some research to trace back the said IS-2 mount as well, and here's what i found:
Mount only appeared on IS-2's with the directive №6723cc dated from 14th October 1944. Older IS-122's (IS-2's) were (or were not, case-by-case thing) retrofitted with said mounts. Starting from 1.01.1945, all new IS-2s had the DShK mount.

Source used:
Mikhail Svirin "Танки Сталинской эпохи. Суперэнциклопедия. «Золотая эра советского танкостроения»", p.546

Spoiler : Scan of said page :