While my classical history is more than rusty!!! it is of course well known that Toledo from the earliest times was well reputed for its fine steel. It does seem as Philip notes, that the Roman gladius was adopted in form from the double edged swords of the Celtiberians, which had evolved from the swords of the Hallstadt culture.
I cannot say I know a great deal on the gladius itself or the various forms, as Philip notes, the Mainz and others, but it seems certain that the metal working techniques were enormously benefitted by the character of the ore resources.
With the advent of Muslim rule in Spain in the 8th century, and the many Damascus smiths who were fleeing Syria into Spain, the steel forging skills excelled.
It seems like in the 16th century the moving of the royal court from Toledo to Madrid had a detrimental effect on the industry, and by the latter 17th century the craft was virtually demolished. With the dissolution of the guilds there had been efforts to have foreign makers augment the faltering industry. In Solingen, they were having their own difficulties after the devastating Thirty Years war, and I think that this, as well as the need for smiths in Toledo, may have been the reason for numbers of German smiths actually going to Toledo.
Still, the makers in Solingen were using spurious signatures and marks playing on the well established reputation of Toledo.
While Valencia was certainly a noted source for blades contemporary to Toledo, in fact some references consider them superior , but the production there was much smaller in scale. It does seem worthy of note that when King Carlos III decided to try to revive the industry in 1760, the only place he could find a master craftsman with a few others was in Valencia. By 1780 the royal manufactory was engaged and in Toledos outskirts, but did not reach the former glories of its heritage.
Still, the sound of 'Toledo blade' certainly has that fantastic ring to it!!!