I've recently read that swords with threaded tangs existed at least as far back as the Renaissance, which surprised me because I've always thought of it as a modern construction method. However, the only examples I can find are hangars and military sabers.

While reading the review of Del Tin 2150 I noticed that "a pommel nut and rosette-shaped plate adorn the top of the pommel" (in reference to the original). Is the "nut" in this case a piece of hardware which secures the tang to the pommel or some sort of decorative piece? When exactly did this type of construction arise?

In the Gladiatoria manual (mid 15th c), there is a plate showing a heavy fighter unscrewing his pommel and throwing it at his foe...
The merit of the tactic aside , it certainly shows that the consept of threaded pommels was known.

Please check out these previous threads on the subject and consider adding to one of them instead of creating a new line of discussion:

http://www.myArmoury.com/talk/viewtopic.php?t=25139
http://www.myArmoury.com/talk/viewtopic.php?t=16868