Kriegsmarine headphone with marking

[gebirg98]

Hello
I have this kriegsmarine headphone with curious marking
F.Sch.Ngb
I think F.Sch for Fernschreib but Nbg
Can you help me
Regards

[glaser]

Fern Schreiber xxgerät?

[Val]

Intrestingly enough, lot's of postcard have the same markings F.Sch.Nbg.