I believe the IIIc was made from 1940 to 1951, and would be authentic for the period if it was available during the early part of the war. It likely would have come with a 50mm f/2 Summitar which was made from 1939 to 1945. The 50mm f/2 Summar was discontinued in 1940, but was probably used where the newer lens was unavailable. During the war photographers used whatever they could find. I knew one GI who found a lens and shutter, and made a camera body for it.
Eugene Smith used at least a Contax and a 6x6 Zeiss folding camera in combat. When he left the States as a war correspondent in 1942 he insured the ten cameras he carried. On one assignment aboard ship in 1943 or 1944 he carried three TLRs, a Kodak Medalist, a 4x5 Graflex, two Speed Graphics, and a Contax with five lenses. Not all photographers were so well equipped. The Army contracted for rather basic 35mm Kodaks for some photography.