I just wanted to join in to admire this outstanding sabre! I know that in noting material pertaining to naval situation during the American Revolution here my notes will be superfluous as you know this stuff inside out! but I will anyway as its how I learn.
As Gilkerson (p.111) points out, "...during the American Revolution almost all Continental Navy officers used swords of English or European pattern and manufacture as the Colonies had little capability to produce blades of quality".
Actually I think personally that it was simply that the American navy, rather than being a standing service with ships of the line, was mostly small ships often commercial with letters of marque issued by congress. Obviously the Bon Homme Richard and John Paul Jones come to mind as one of the exceptions. Privately held weapons were of course already in place and the volume of British and European weapons available as opposed to the very small number of swordsmiths active in the Colonies. These makers, though only several, were more than capable of producing good quality weapons in those times.
In Neumann, there is an example remarkably similar to yours (p.108, 140.S) which is English c.1770-80. The lionhead, like yours, is characteristically British in style, and the also British style slotted guard has multiple slots a bit different. The blade appears of the same cross section and curve of yours.
I think that much as in most cases looking for maritime potential with swords of these times, unless they are with fouled anchor as with examples of British navy of the period or otherwise distinctively decorated, we can at best equate the sabre as of the type likely used. Considering the number of small vessels privateering (up to 600 British ships were seized) there is certainly every possibility of this sabre, or examples like it being used by those Americans on these vessels. The navy was disbanded after the end of the war until the Naval Act of 1794.
Again, all of this is added here for my own learning mostly, and for readers here, you guys already know all this stuff
All the best,