Hi Freddy, on Westerdijk's book there are two drawns of similar daggers-short swords in the XIII Groep (2-3) lulua-songye-luba. Something that could be similar with your piece is the sword on Fischer-Zirngibl, but is attributed to the Tchokwe (

). On Waffen aus Zentral Afrika there is the most similar and is attributed to the luba. So it's clearly of the southern area of Congo