This should be from the Cameroon border region. This was sold earlier this year at auction with another (straight bladed) takouba and both have wound up on eBay.
I've had a few of these over the years and if I'm allowed I will post a link to where you can view a few others.
http://takouba.org/catalog/index.php.../curved-blades
Sword #90 on that link I posted on the forum a while back and is quite similar to yours. I like these, they have a nice feeling in the hand. The curved blades are a rare, but known element of takouba design.