Nando, you have set some well placed questions, and trust me, Sir James would be delighted that the subject would be challenged and looked into further! This topic is profoundly daunting, and it is easy to see why these matters are seldom adequately addressed in discussions.
It is complicated, and I have spent days now poring through every resource I have....the bookmobile looks like an explosion in a library
First I will note, it was not James Mann who made the allusion to the questioned Hernandez lineage, but Eric Valentine in his book "Rapiers" (1968).
On p.67:
"...the Hernandez family were Toledo swordsmiths . Sebastian Hernandez the elder worked approximately 1570-1600; Pedro the younger was working 1610-1630 and Johannes in 1660."
As can be seen, the chronological lineage might easily suggest the family connection, but it is puzzling since Valentine cites Calvert ( "Spanish Arms & Armour", 1907) which contain Palomares punzone plates. As noted, in those plates both Sebastian, elder and younger are imaged and both with a crowned '3' as their mark (even more strangely Mann, p.281, remarks that this mark is a crowned 'Z'!).
While Valentine made the suggestion of this presumed Hernandez lineage, it was apparently derived from Mann's index in reference to these makers with same names. What is notably absent is any reference to Sebastian the younger as far as I can see, yet Pedro and Johannes are indeed represented.
In Palomares there is yet another Hernandez shown which does not seem to be grouped with the elder and younger Sebastian's, that is Roque whose punzone is similar but a crowned 'S' (#88).
I believe these conundrums have become complicated due to the interpolation of markings and names used by German makers who were as well known using Spanish names and marks. As well noted, it would seem that Pedro and Johannes would appear in the Palomares register, and that authoritative reference is the source for the secondary Sebastian, who does not seem to occur in other sources.
Wagner ("Cut and Thrust Weapons", 1967, p.186, pl. 6) has a rapier shown with PIETRO HERNANDEZ inscription and the note that he "..lived in the first half of 17th c in Toledo". Here he is noted to have used the crucifix as his mark (re: Boeheim, 1890, p.669). In Boeheim he notes Pedro on that page, but shows a curious collection of his marks....a crowned P; a crowned F; a faced crescent moon and most telling, a crowned S over T.
Nowhere here is the crucifix other references attribute to him.
As is well known, the crowned S over T is seen in Palomares as that of Tomas de Aiala (Mann, A567, A643) in #93. However, Mann, A532 has this mark but with SEBASTIAN HERNANDEZ inscribed. That particular blade is noted as probably a German imitation c.1620.
Mann (A652) notes on p.331 that "...as well as using the half moon mark, the Stantlers of Munich also employed the crowned S over T'.
Valentine notes a well established fact on p.66, that the TOMAS DE AIALA name had become used as a trademark.
In checking "German Swords and Swordmakers" (Bezdek, p.154) we see the crowned ST as the mark of Christoph Stantler of Munich, 1607-1643. Here we can see other Spanish punzones in several cases used by German makers as their own. Other instances abound with these Spanish names often with other marks not in Palomares It is noted that Pedro used the crucifix, but that this mark was similar to other German makers (Cleles and Col). Col was of course Enrique Col (Heinrich Col) who was a German maker in Spain (1590-1610 per Wagner p174)...who incidentally often used inscription MI SINNAL SANTISMO CRUCIFICIO ( my mark is the crucifix).
Mann, A533 notes that Pedro Hernandez, the younger, in addition to his crowned '3' worked in both Toledo and Seville and used the mark of a 'wild man'. According to Mann (p.327) and Bezdek (p.138) this mark is that of Johannes Hoppe of Solingen c1630, but some references show range 1580-1645.
It is worthy of note that by 1561 the economy and in league, the trade in Toledo had begun to deteriorate due to the Royal Court moving to Madrid, and by 1664 the economy and trade in swords virtually in ruin (Cohen, "By the Sword", p.115). Here can be seen the movement of makers to other centers and the developing alliance with German makers. It is well established that fine armor from Munich was entering Spanish courts, and that the Stantlers were using the reputation of Spanish sword makers quid pro quo does not seem surprising .
There are so many other instances and cross references that it would be fruitless to try to add it all here, with the apparent interchangeable use of marks similar or nearly identical by Spanish makers and interpolation with German smiths making these kinds of sound assertions in tracing lineage and actual makers difficult at best.
Gav, thank you for adding that beautiful blade!!! This is a great illustration of these Spanish names being used as quality trademarks in Solingen, and by the time of these swords in the 18th century it was profoundly Solingen supplying the blades.
If I may add my thoughts to the question concerning Italian style hilt etc.
Much of Northern Italy was provincially part of Spain, and Spain typically looked to Italy regarding fashion in arms and armor. At the same time Germany was rather in the middle in production of arms and it would seem factored in the Italian style while using Spanish names . It was noted by Walter Karcheski on the armour worn by Spanish conquistadors that more often than not, the much recognized morions worn by some Spanish officers were actually Italian. Again, returning to Munich, some were German.
References: "Waffenkunde" Vol. VII, Wendelin Boeheim, 1890 , Leipzig
"Cut and Thrust Weapons", Eduard Wagner, Prague, 1967
"Wallace Collection, European Arms & Armour", Sir James
Mann, London, 1962
"Rapiers, Eric Valentine, Stackpole, 1968
"German Swords and Swordmakers" R Bezdek, 2000
"Spanish Arms and Armour" Albert Calvert, London, 1907
" Arms & Armour" Auguste Demmin, 1877, London