Nice piece, Wayne! Don't know how I missed this one! I support the others that believe the original brass slot hilt to be French. This pattern was used on the French naval officer's pattern slotted sword with the 'swinging' knuckle bow as well as the French cavalry piece. It had the same circular decoration to the slot openings and same stark angle to where the guard and knuckle bow meet. American Rev War swords were predominantly parts-swords, made from European blades and often salvaged parts. As already pointed out, it is evident that this brass guard once had branches cut away (if it were the French naval officer's sword guard I mentioned, that would make sense.) I feel this is absolutely of the period and a weapon assembled by the Colonists in the desperate times of war.
Here's an old thread featuring one I used to own-
http://www.vikingsword.com/vb/showthread.php?t=18540