What a fine piece!
I do love these mystery pieces and the detective work that happens when one is posted.
I looked at the pictures before I read your history as I wanted a clear first impression.
Looking at the pommel, the fine engraved wavy lines reminded me of late 18thC and 19thC items with simple mechanically added decoration. Rather an elaborate pommel, nice and big to hopefully bring the point of balance to the right place.
Big steel collar at the top of the handle? Thats a bit 'sudden' Handle seems rather on the long side, plain, wood has an age split, can't see any holes or evidence of previous wire binding?
Quillons/guard/counterguards! Hmmm, Rather elaborate and nice! Steel, difficult to work, business like and not overly fancy, but certainly attractive and stylish. Rather good, getting more interesting! Quite heavy and the 'guard' elements almost look like they are soldered to the quillons?
Looks quite heavy, almost like it would be more at home in a basket hilt than swept.
By now I'm thinking its a fancy continental (Spanish) piece, Nice and heavy fair quality, possibly for work out in the colonies. Date... omg... I don't know. Late 18th to mid 19th?
Post 3 musketeers, pre El Zorro!
But I'm imagining a chap rather like Ricardo Montalban carrying it (from the Zorro film)
Then I read your story! So I think that fits.
How about some better pics of the blade and close ups of the hilt?
I'll be interested when the really knowledgeable members arrive to pin it down conclusively.
BTW, I love it!