Mauser C-96 (broomhandle) serial starts with 464 indicating manufacture year between 1921 and 1923.
In 7.65 caliber 

The distinctive characteristics of the C96 are the integral box magazine in front of the trigger, the long barrel, the wooden shoulder stock, which gives it the stability of a short-barreled rifle and doubles as a holster or carrying case, and a grip shaped like the handle of a broom. The grip earned the gun the nickname "broomhandle" in the English-speaking world, and in China the C96 was nicknamed the "box cannon" because of its rectangular internal magazine and because it could be holstered in its wooden box-like detachable stock.