WW1 German “42er Deutscher Brummer” Close Combat Knife

I just purchased this family heirloom knife from a neighbor who is retiring. He told me that his family is from Germany and passed this knife down generations to him. The knife measures 10” long and appears almost unused.
Marked on on side of the blade only with “42er Deutscher Brummer (D.R.G.M.)". The handle is genuine stag or deer antler.
“ Original WW1 era “Deutscher Brummer” type Kampfmesser (close combat knife) manufactured circa 1914-1916. The acronym D.R.G.M. stands for Deutsches Reichsgebrauchsmuster – it means that the design was officially registered in the centralized Imperial registration. The “42er” shell design refers to the huge German 42-cm (420-mm caliber) “Big Bertha” super-heavy artillery piece fielded and used by the German army with great success against the allied fortifications in Europe.”