[Jim McDougall]

Well done Bruno!!
That example REALLY looks like yours! and while I cannot make out the scribed letters in the remarkably similar 'dumbbell' cross guard, it is tempting to think they may be another grouping of the 'field' type inscriptions on these swords.

The book on American Revolutionary war swords comprehensively illustrates many examples of the swords in use at the time in America. Not surprisingly there are many from assorted European countries, and actually numbers of these were from Spain. Spain actually was indirectly involved supportively in limited degree with the Colonials, as was France of course, sharing their ever present friction with England.

While it would be good to establish from a corroborating source that these brass lionhead swords were indeed French, it does seem they were somehow present in North American context, here appearing in two disparate sources.

Returning to the interesting markings, the subject of the thread, my references to the possible abbreviations of the lettering here are admittedly inadequate specifically, however they reflect a style of combinations which were used on Mexican arms (and uniforms) I have seen. These notes are from researches many years ago and frustratingly incomplete, but the gestalt of the groupings was to me, compelling.

During the American Revolution, there were swords such as 'bilbo's' and other types of Spanish colonial swords which turned up in American context as shown by Neumann. With France as an ally, again in degree, these swords could possibly have turned up here, however with these markings it is more probable that they turned up in Mexico in the acquisitions of 'surplus' after the end of the Napoleonic campaigns.

These materials were being dispersed not only by France, where the artillery acquired by Mexico originated, but by England who was dispersing much of its firearms with cessation of war by 1820s. Napoleon was defeated, and of course not the source of war materials to Santa Anna nor Mexico,....it was simply that Santa Anna admired him.

While these abbreviations and conventions in writing may have been in similar presence in Iberian context, the crude character of their application seems more in accord with the colonial and often remote Mexican possibility than Peninsular, where better facility was available.

Regarding the possible identity of the abbreviated (presumably) regiment on the guard of the OP sword, the 'R' may of course be 'regimento' but the 'F' is unclear. If it was to the name of the unit (honoring heroic officers etc. it is hard to isolate. The N and o would be numero (sword #) ...6, but the next 'F' is unclear.....but could be to fusiliers (?) .

Attached is the image of the sword identified as American Revolutionary war linked in post by Bviera. The indiscernible markings are crude much in the manner of the original example here, but suggest similar context in their application.