The side of the knuckle bow facing the fingers is broad and flat. No other model 1840 cavalry sword hilt has a knuckle bow like this. The branches are wide and flat. The surface of the guard facing the blade is flat, there is no rim around the edge. Where the grip meets the guard there is a raised piece that is similar to a ferrule. The rim around the pommel cap is thin. The quillon is somewhat pointed. The grip itself is cord wrapped in the style of those of the sword makers of Solingin.
As for the blade being absent of markings, I have seen numbers of blades with marking in various states of being polished away. I have seen swords with no blade markings but markings on the hilt identifying sword with no signs that the blade has been re-hilted.
I have seen swords painted with silver and gold paint that used to hang in GAR halls. Have someone check the knuckle bow with a magnet. If the hilt on this sword is brass it is a new variation of a PDL sword that has not yet been identified,( based on what I read in Thillmann's cavalry sword book.)