[Jim McDougall]

I finally received the copy of "Treasures of the Caribbean" by Rodney Hilton Brown (2023) and it is an intriguing compendium of various stories and circumstances in Caribbean history often with cited references .Unfortunately this entry showing what appears to be the same pattern in hilt and blade, does not cite such reference, (p.279).
The blade with same fullering carries the Spanish motto, suggesting the swords were apparently inscribed independently.
While the date/period indicates c. 1720, this is incorrect as this is a Napoleonic period sword.

After some time of going through "Les Sabres" by Jean Lhoste and Patrick Resek (450 pages) I found no comparison as far as the hilt form, and this book is incredibly comprehensive.
I did find that the flaming grenade device was indeed notably present on various hilt form, typically amidst hilt guard assemblies in cartouche, some singular on stirrup hilt sabers, of grenadiers and gendarmerie, as noted.
However I found no cases of these grenades used at root of arms of multi branch hilts as seen here. The style of the branch system suggest in my opinion that this is most likely a limited issue of Spanish officers sword c.1800-20, and of course clearly influenced by French forms. As yet, no match in references on Spanish or Mexican sword form references.