Hey Ronski, I did some research on that marking and found it may have been WW2 era stuff. The marking was related to this:

M7/28 Gustav Felix, Gloriawerk, Solingen That maybe an RZM number on the razor.

This list was an extensive bunch of makers that were on a list to supply the Germans with Ordnance. Possibly in steel productions.
Seems possibly a part of a German Labor party.

Any manufacturer that wanted to manufacture items for any of the NSDAP organisations had to apply for a RZM number from the Reichszeugmeisterei der NSDAP (RZM). This number was then stamped on all the items manufactured and if the quality was not satisfactory the RZM could withdraw the number.

Hope this may help shed some light on it.