Good catch Victrix! The structure of this marking is very much like those seen among the marks typically attributed to Passau makers, which unfortunately are mostly unidentified and of the latter 16th century. These devices are somewhat similar in convention in having 'arms' in various configuration (Kinman, 2015) much like the familiar 'anchor' markings from Spanish sword blade motif then copied in Solingen.
These often have subtle variations in similar fashion in the cross bars.
Without going into the complicated analysis of developing of arms markings, and noting the excellent parallels noted by Victrix in these 'house markings' which seem inextricably linked, I think we can presume this to be some sort of commemorative application.
It is crudely applied in comparison of course to the characteristically applied acid etched motif in accord with latter 19th century military dress swords, so very much out of context.
I must admit, the choice of one of these mysterious (because few are singularly identified) markings on a late period military sword is most unusual, and might have some association with a military fraternal organization or something in those areas. Perhaps in the Masonic type genre.? With these the use of very early symbolism is often favored.
Just thinkin' outside the box I guess.
The idea of it being a monogram as described is very plausible as well, if the top parts of the letters are in fact missing...it would take more forensic analysis to determine that.
Whatever the case, a beautiful sword! we dont see a lot of Scandinavian swords here!