This Dr. W. Gérard B3x sniper scope has an uncommon transitional straight lined mount. These mounts didn’t allow to aim with the rifle regular sighting organs. That’s why they were replaced by deported mounts on most of sniper scopes pretty early in the war.
This ZF39 type scope was made by K. Kahles in Wien. These 4×60 sniper scopes were given the code “cad” during WWII. They were used on SSR, LSR and high turret mounts (like this one).