Hi Detlef,
This type of "brazil nut" pommel can be found on takouba from various ethnic groups, but is an older style (pre XXth century).
Determining where a takouba was made is, in my opinion, always a game of guesses. Some details lead me to think it is an Haussa work, but I could be wrong.
It seems to me that this kind of big boxy guard, with engraved decorations and tin (?) wash is more usually associated with the Haussa (Tuareg ones, for example, are usually slimmer, with a different shape). (See this one for example :
http://takouba.org/catalog/index.php/takouba-109)
Locally made blade that are on the larger side usually seems to be Haussa, like this one. (See here :
http://takouba.org/catalog/index.php...usa-people/132)
The type of mounts on the scabbard is also usual for this group, with some really long mounts (the type of decoration and the tooling on the leather kind of looks like Haussa to me too). (Again, example here :
http://takouba.org/catalog/index.php...usa-people/132)
Those are some of the hints (but also the general look of the sword), that makes me think it could be Haussa, but again, it's hard to be absolutely sure, and I could be wrong !
Regarding the edges, I meant to say "tranchants rapportés", but I don't really know how to translate it to English, so periphrase, here I go ! The forging flaws following the edges of the blade almost make me believe that it could have been made using three metal rods (two hard for the edges,one soft for the core) that would have been forge welded before shapping the blade itself, like it was done on some medieval swords. Although, I have very little knowledge about african metallurgy and don't know if they used (or even materially could use) this technique.