Marc would like to be able to say something about the marks, but he can't
It's a small brass inset what I seem to see in the mark closer to the hilt in the reverse of the double "B" (fifth picture, DSC00010.JPG)? It may be an optical effect...
I'm still looking around for it, but as a first approximation it's indeed Spanish/Spanish Colonial. It's not the first one I see, with some minor variations. Blade seems to be "import", probably German. It's a military sword, Cavalry/Dragoons, second half of the 18th c., and a nice piece to boot, my sincere congratulations