stamping on an 1906 variation navy, pls help ..

[Ron Wood]

Wolfgang,
This "pinwheel" mark is an inspector's mark usually found next to the recoil lug on the bottom of the receiver. It is also found in that location on the 1906 Russian and Bulgarian model Lugers from roughly the same time period as your Navy. So while this marking is not common it is not unique to your gun.
Ron