Kriegsmarine metal box

[Watchdog]

Thats best quality photo i can do:

Yep, I believe that is a KM stamp for sure. Also, for what help it is I have seen similar engraving on other KM items (including war badges and EKM etc). It is done in a workshop with a machine mounted rotating tool similar to a router. Just the kind of gear in a marine workshop on shore or on larger ships where fabrication of parts requires precision machinery.

Regards

Mark