Hello Hendrik,
I have no idea about the year, but I guess the picture was taken in 50s or 60s years. I have found also one more picture of the same vehicle. According to the bilingual (russian and some latvian or lithuanian?) advertising sign on the shop it would be some Baltic republic of USSR. Concerning the vehicle, the second picture shows it is 4x2. Because the rear body seems to be Russian, as you mentioned, my guess is the original vehicle is GAZ-51, which would correspons also with the rear split differentioal housing visible. And as for the Stude cab, the reason could have been that the driver ended up, after drinking too much of Vodka, in the forest and needed some substitution for the damaged one
Happy searching, Jan
