Königlich Gewehrfabrik or Royal Rifle Factory in Erfurt. A prolific producer of rifles as well as many edged weapons. The bayonet appears to be a First World War period S.84/98II. Erfurt produced that model from 1915 - '17. Some were also finished from blade blanks provided by Gebrüder Heller and will have both maker's marks.
S84/98nA date should be on spine, there are remains of nickeling on blade, so probably postwar used as a dress piece. These bayonets are not rare,second quantitative modell after S98/05 butcher bayonet probably by Germans in WW1.b.r.Andy
Mostly german export S84/98 delivered post 1936 to Spain, some are 255xxx marked. should be cleaned a little and oiled, other possible marking is a scribed letter "o" on lower spine of blade near crossguard on place when the edge ends. By removing grips there could be WaA253 on tang.b.r.Andy
Königlich Gewehrfabrik or Royal Rifle Factory in Erfurt. A prolific producer of rifles as well as many edged weapons. The bayonet appears to be a First World War period S.84/98II. Erfurt produced that model from 1915 - '17. Some were also finished from blade blanks provided by Gebrüder Heller and will have both maker's marks.