Thanks very much Norman
You're right, arms collectors and scholars in the Victorian period indeed loved to embellish and romanticize, and the colloquial terms and folklore they applied to many weapon forms have remained firmly in place to present times. The term 'claymore' has brought considerable attention as well, and it has often been argued that the word referred to the huge two hand swords in use before the development of the distinct basket hilt swords. Claude Blair (in "Scottish Weapons and Fortifications", ed. D. Caldwell) has noted that in actuality the large two hand sword was termed 'claidheamh da laimh', while the basket hilt was called the 'claidheamh mor' or loosely 'claymore'.
The basket hilt with curved blades I believe were termed 'turcael' (presumably referencing the curved blades on Turkish sabres the Scots saw when on campaigns in Eastern Europe) and did of course exist, though it seems relatively sparingly. Obviously the inspiration for these basket hilt sabres may well have come from the Northern European heavy sabres described in the 'Sinclair' reference, though probably from the regular interaction in these regions by Scots. I agree that it would be more than difficult to draw any line of progression from any specific source of influence for either the basket hilt, or for these curved blade types.
In the 18th century, when basket hilts of Scottish style were being made for the British cavalry, there was a standard form hilt with conical pommel, and I remember one of these mounted with a British M1788 light cavalry sabre blade.
Interesting reference to the use of the basket hilt on sea service swords, and I have long believed that these would have been ideal for protecting the hand in close quarters melee aboard ships. Contrary to modern ideas of the basket hilt being shiny bright metal in those times, the hilts were typically russet brown or japanned, to protect the metal in the dampness of the Highland climes. These would have added to favorability.
As mentioned on the "pirate weapons" thread, the notorious Blackbeard actually met his end by a Highlanders basket hilt in shipboard combat...not at the hands of the British officer given credit for his death.
I think you make a very good observation in noting that these varying types of swords were probably all very much contemporary, and the huge two handers were still seen in use in minimal degree through the 17th century. As the baskethilt developed, the earlier sword forms certainly remained in use as well . There were no means for mass production of swords, and they were certainly expensive and beyond the means of many clansmen. I often wonder if many of the heavy blades from Germany on the earlier baskethilts might have come from Scots returning from campaigns on the Continent, and led to the predominance of these blades through ongoing trade.
All very best regards,
Jim