Spanish Rapiers, a Bilbo FYC.

[fernando]

Some (most) times is easier to be told what specimens are not, than what they are. So many weapons are a mix of styles ... whether added within time or originaly intended by the maker. A significant quantity of my stuff falls into that area .
It appears than in (Iberian) typology, you have the 'sword' as so called, belonging to 'military' universe and the 'rapier', that of 'civilian' development ... although also used by military, in determined contexts. Two (of the?) sympthoms which indicate that the piece is a rapier are, the blade being narrow (er), more vocationed to fencing and the knuckle bow being loose, and not screwed or welded to the pommel, a detail not neglectable in Ordnance combat examples.
So your specimen could be called a rapier, although with some military features like, i guess, its guard, typically called boca de caballo (horse mouth), as already mentioned here by the connoisseurs.
A couple forumites can tell you that this guard did not exist till the beg. XVIII century; therefore a pattern later than the (beg. XVII century?) grip. Then if you fix the grip date as being originaly assembled to the (imported blade), you will find that the Sahagun legend is not the maker's mark but an allegory to him, to add value to the blade. This way you could say that, basically, this is a XVII century rapier, with a later military type guard addition.
I don't beleive i dared to adventure giving a presumptious opinnion in such matters..
... Just forget it
Fernando