A quick chime in, damn busy those days...
Hi, Fernando. Funny, I discussed this piece with SOMEBODY in February 2008. I would have bet money it was you, but my mind is starting to play tricks on me...
Anyway, it's indeed Spanish colonial, I've never have seen them attributed specifically to Mexico, nor seen any with a mark that could make me think they could be, but, of course, I'm limited to my own experience
Those are XVIII c. and for use by cavalry and/or dragoons. The guard is a variation of the Spanish 1728 pattern for cavalry. No idea about the marks, though, I'm afraid.
A beautiful exemplar, though, if I may say so
Best,
Marc