Hi Iain,
Im pretty sure you are well aware of what the hilt is!! "
I thought I would try to get ahead of the stampede of responses here with what I think the blade is. Surprising this never sold...must have had a pretty steep reserve, but this is a remarkable blade.
When you suggest this is French, I am wondering if there were other clues in the description or close ups of the engraved panel and motif. Actually the suggestion is well placed, as these kinds of motif and forte panel were a popular style in the late 17th into 18th on Continental cavalry swords for officers.
The style of the motif does remind me of the Caissagnard type of Nantes in mid 18th but certainly was known before that. It existed on hangers in England in the previous century.
It would take considerable review of catalogs and auctions for finding close match.....but at this point I would say...cavalry officers broadsword, Continental Europe, early 18th or late 17th.
Extremely nice seeing these very old blades in the Saharan context, setting in mind many fascinating possibilities!
If anybody out there has the Christian Aries series on French swords there might be a match.