[Jim McDougall]

This is an interesting example of the general type of hilts found on hangers and cavalry swords (typically associated with 'Walloon type) with bilobate counterguards in the 18th century, usually second quarter to mid. While unable to find an exact match in some of the German and North European references at hand, it follows the general style indeed seen with German forms.
Though the blunt ended quillon suggests those origins, the thumb ring usually present is notably absent. Naturally by this time there was distinct movement away from this feature it seems many, if not most, examples from Germany and Europe in general had them.

One of the best references I know for these kinds of weapons is "Swords and Blades of the American Revolution" by George Neumann, 1973.
In going through this I found many remarkably similar examples, mostly in the hangers with hilts of the bilobate form. As noted, the bilobate 'walloon' type guard became extremely popular after the Thirty Years War (end 1648) and developed in the Low Countries (hence 'Walloon') . By the mid 18th century they became well known throughout Europe, and by the time of the American Revolution they were profusely represented. Neumann notes (p.76), that at this time, "...more than 30,000 German mercenaries carried a motley array of early and late European arms".

It is also well known that Germany was of course supplier of swords and blades to the British army, these types included. In most cases it seems that the British favored a rather heart shaped bilobate guard, while the Continental types were relatively true dual lobes.

What I found interesting in checking through the examples in Neumann was markings, typically on the underside of the counterguard as seen here.
While it is tempting to think of the FA as Friedrich Augustus II , Elector of Saxony in these times, I think these letters more likely regimentally noted.
On the examples in Neumann there were many combinations, it seems invariably on counterguard underside and most British (a couple of American). Many were referred to as 'common British fraction markings', such as 9/56; 2/48 etc. Others has an RA; No.9: 28 but most telling was one reading 'R No.9' .

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In looking in Wagner ("Cut and Thrust Weapons", 1967, E. Wagner )Plate 7, p.257 is a Saxony Dragoon sabre end of 18th c. and at the forte is the monogram F.A. surmounted by a crown and No. 104.
This monogram is noted as Frederick August (Elector of Saxony), and the number combination in similar form to this example.
The sword in plate 7 is not the same but the initials and numbers seemed to be pertinent.

I would then reassess my view on this sword as probably a Saxony dragoon sword mid 18th c. and quite likely among the arms brought into America with those German mercenaries previously mentioned.