Hi Kirk,
The Manding as a linguistic group rather than an "tribe" per say, is well noted. They are an extremely diverse group of peoples found in an extremely wide ranging area.
Unfortunately I an not aware of a typology or solid guidelines for range of hilts encountered among the Mande ethnic groups.
The only real generalization I can think from my own experience is the propensity among Manding swords for a terminal on the pommels. There is of course a little nub on the end of your sword and the 'nubs' which are seen on Manding sabers (by this I mean the swords that are often European cavalry sabers with simple leather hilts and a brass nub) as well as swords from Liberia or Ivory coast with wooden hilts and again a small metal nub. It seems to be a motif that recurs frequently.
Lew brings up an interesting point with the Dan or Gio people attribution for the drawing you showed. The Gio are of course a Mande speaking people. However I always thought they were centered in Liberia and Ivory Coast... Not Senegal. However I could be wrong, perhaps Lew can clarify? Otherwise, purely from the drawing and the caption in the book of a Mandingo chief, I would assume the Mandingo group of Sierra Leone?
I have to admit to having little experience with any of the Mande ethnic groups and their weaponry, but I want to state again that this is a nice piece. I suspect as well it might be a shortened blade, but that in no way detracts from it.
I wanted to show off a few other examples but needed to wait until the auctions ended. I am uploading a couple photos as well as the links. Sadly this first link I forgot to bid on. A very similar piece to yours, although shorter.
http://www.ebay.com/itm/260907280936...#ht_500wt_1301
And the second, a set of two that has similarities in design of the hilts although executed in different materials and perhaps a bit newer.
http://www.ebay.com/itm/180771133588...ht_1507wt_1298
Hopefully some of this is some use, I only wish I could give more clear answers or directions.
All the best,
Iain