Thank you for sharing your "Deutscher Brummer" illustrations and information!
... This knife was also available and listed in a 1930's Anton Wingen Jr. catalog and these knives have "(Ges. Geschutzt)" below "DEUTSCHER BRUMMER" instead of "(D. R. G. M.)" and have a black snap button that has no design?. I do not know what makers mark these knives have but would guess it is the # 6 makers mark with "ANTON WINGEN JR." above a standing knight with sword and "SOLINGEN" underneath. ...
I am off from home and have no access to my complete archieves right now. Anyway on my computer I am listing a 1930 Anton Wingen folder with this illustration:
More than one decade has passed since the end of WWI, noone is being alerted that WWII might begin sometime under NSDAP/Nazi regime. So note Anton Wingen's description as "beliebtes Pafadfindermesser" (in English: pupular boy scout knife)!
... Also note that in the 1915-1918 period and maybe later, these knives were also made by J. H. Becker, Solingen. See J. Anthony Carter page 92.
Anton Wingen Jr. was one of very few Solingen cutlers with an own drop forge for forging their own blade blanks. Such 'J.H. Becker' marked "Deutscher Brummer" knives surely were being made under contract by Anton Wingen cutler exclusively for J.H. Becker. Even if Wingen's DRGM protection rights might have been expired, making dies for such a blade pattern would not have been an economicly task for competing other Solingen forges.
regards
chevalier2022