As always, identification of North African weapons is a conundrum, when considering trade routes, interaction of nomadic tribes, constant refurbishing of older weapons and eventually, the curse of the tourist trade!
Katana has well pointed out the clear Hausa influences in this dagger, and it most certainly may be, or have been Hausa. It appears to have had, as noted, a sheath made as a later addition. The strip of crocodile hide at the throat of the scabbard suggests possible Darfur association, as this feature is typically found on kaskara mounts from there. The Hausa groups seem to have inhabited regions from Niger, westward as far as Sudan, therefore the refitted dagger may have found use in these regions.
Best regards,
Jim