Pepe
You might want to take Bill Wlyonâ??s advice, from your picture it looks like your bore is less than 8 mm and that would make it a 7.65 caliber.
I am going to default back to the other collectors on the cartridge stampings, way out of my knowledge area; the only one I might know is the DWM K and this is a guess.
DWM K = Deutsche Waffen u. Munitionsfabriken, Karlsruhe, Germany
Thank you for letting us analyze your gun, its fun to do research, donâ??t be a stranger on the forum we can always use a perspective from your area of the world.
If you still live in Portugal or have contacts there I would love to make contact with the Lisbon Maritime Museum and ask them some questions on Navy Lugers. There is much research yet to be done.
You can email me directly with any information:
vern_t_2000@yahoo.com
thank you
Vern