Hi Stephen,
That's a quite old 19th century takouba in the southern style. Two similar ones can be seen in the Museum of Natural History collections:
http://anthro.amnh.org/anthropology/...%20%20126%20AB
http://anthro.amnh.org/anthropology/...%20%20127%20AB
Both examples have a Nigerian attribution. Given the recent discussions Jim noted about the cross influences of kaskara and takouba in Hausa areas I would think it fairly safe to say yours could be from these northern Nigeria regions.
I would not assume that yours had brass plates, as you can see in one example I posted it appears that rivets hold the leather in place on the guard.
Can I ask if the sword is in your personal collection? I would look forward to seeing detailed shots of the fullers, half moons (I assume they are present?) etc if you could post such details.
Best,
Iain