Gonzalo,
On Forton:
You make valid points and I too have picked up on some things in Forton's books that left me scratching my head. But then, I can pretty much say the same about most books that deal with similar subjects.
Writing about old knives is not of mainstream academic interest, and the task usually befalls upon enthuisasts with limited resources who work for the sheer love of it, for there is no financial reward in such research.
I should add that Forton is a Spaniard, who is university educated and as of recent, had a collection of some 500 pieces, considered by many as the best in the world. And this collection has been acquired by the Albacete cutlery museum, so he was much better positioned than most who did, or would venture to study this subject.
So all in all, with whatever perceived faults his works may have, Forton is the best we have until someone comes along and writes something better. However I do not think that this is likely to happen because he gathered all the readily accessible data and it will be very difficult to improve on this, other than write additional footnotes or make minor corrections. And I should add that all the other serious writers on this subject use his works as the point of departure. Of course, what should have happened years ago was a revision of this book, but so far nothing has come to pass.
On the subject of pre 18th century navajas: As I said in an earlier post, the hard evidence is missing and this pushes us into speculation territory.
There was a thread here some five years ago re a paper discussing navajas found in a 17th century galleon. Unfortunately, the author of the paper did not produce any evidence of what we call these days a navaja. See
http://www.vikingsword.com/vb/showthread.php?t=15626 and
http://www.melfisher.org/pdf/Navajas...2_Galleons.pdf
Be that all as it may, I did say in my post #32 of this thread that since folding knives have been around since antiquity, what we consider a `navaja' is a matter of arbitrarily identifying it with a certain typology. So, as things stand at present, if what we call a navaja is a folding knife with a more or less large blade, say 5” plus, which can be locked into the open position, then we cannot regress any further back than the 18th century. With all this said, if we include friction folders, then we can probably go back to Roman times.
Cheers
Chris