[machinist]

I recently bought this escopeta at auction and was hoping to learn more about it as this is my first flintlock. One of my areas of interest is the weapons used by Spanish colonists in the south western U.S. and this seems like a slightly fancy version of the sort of carbines that would have been used in that era and area.
What I know so far is that it has a miquelet lock, a Catalan stock, a belt hook and that is about it.
There is a signature of Castano with the last letter partly obscured by the mainspring and several gold lined markings on the barrel breach. One of the marks has lettering that is mostly obscured by the gold being a bit rough and thick but it seems to be three lines of letters with the second and third letters of the first line being NT.
The buttplate is a plain piece of steel that goes about three centimeters down the back of the buttstock. The caliber is .75 and the bore is smooth, there is no rear sight.
I will use the sellers Pics as my camera and camera skill are both pretty bad.
Any information that anyone has, especially about where and when it may have been made as well as how such a thing might have been used, hunting? Defense? Any opinion is welcome.