This is a gray-haired lieutenant of the Red Army Air Force Technical Troops working on aviation instruments in 1944. On the left is a pressure chamber used for calibrating them at different pressures/altitudes. I'll take a guess and say that he's working on an altimeter. He has all the usual tools of his trade: wrench, pliers, screwdriver, oil can ... dewat .50 cal. machine gun round.
He's wearing a hat and a greatcoat over a buttoned tunic over a uniform blouse indoors. Must be chilly. The ratty desk, the paint scheme on the wall and the junk piled against the wall suggest a makeshift lab, maybe in an abandoned schoolhouse somewhere behind the front, but not too far behind.