We've been many times advised by the moderators to refrain to discuss the dealers and concentrate in the pieces. So, I'll try to do exactly that... but
Caveat Emptor, indeed.
This is an European late 17th- early 18th c. sword blade, of the sometimes called "military" type, in contrast with the more slender "civil" types. Probably mounted originally in a Waloon or basket-type hilt, which makes one wonder what the heck does that kind of pommel there. Anyway, the inscription on the blade is the mar of the Giacomo (Gio) Knegt (or Kneght, or even Knetch), an Italian (at least his name seems to hint so) working in the German city of Solingen in that period. He usually signed, indeed, GIO KNEGT / IN SOLINGEN or GIO KNEGT / EN ALEMANIA, with various spelling variations. Many of his blades were aimed to the Spanish market, hence the frequent Spanish version ("EN ALEMANIA" meaning "In Germany") of his signature. I've seen many of his blades mounted in Spanish military M1728-type (what you call "Bilbo"-type) cavalry swords, covering the period mentioned.
All in all, not a bad exemplar by itself. This, of course, completely ignoring the seller's comments about its possible origin.
On a lighter note, well, the market is free, surely enough, but if someone would really be consistently ready to buy these blades for this kind of money, I know quite a few people that wouldn't hesitate a second in dismantling a good part of their collections to supply exemplars...
