Just elaborating on what Ariel has already noted.
This weapon appears to be a ceremonial 'hwi' from Dahomean regions, which were in the coastal areas of West Africa. These are best described in "African Arms & Armour" by Christopher Spring, using material from "Sabres Decores du Dahomey" (Palau Marti, 'Objets et Mondes' VII:4, 1967).
These are, like the 'ada', ceremonial and bearing type swords.
It seems that these areas using the hwi are typically regarded as Dahomean as suggested by the reference mentioned. This kingdom as visited by Burton was referred to as Dahomey. The kingdom of Benin was indeed inland and primarily in Nigeria.
While likely having certain similarities, I think this would be most probably be considered a Dahomean 'hwi'. These swords have a considerable spectrum of variation heavy with symbolic motif. Note the crosses, which may allude to earlier influences from Portuguese swords and seen on early African versions of European swords with such openwork crosses on the quillon terminals.
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