Luc,
Interesting collection and book. Thanks for posting.
There are interesting sources re Central African metalworking. Here is one by Jay Spaulding. He observes (via an 1842 source) that those tribes in Sudan hadn't learned quenching. Are your examples hardened via heat treating or by workhardening the edges.
https://web.ccsu.edu/afstudy/upd15-4...ncient%20Sudan
Also, you may search for "Did They or Didn't They Invent It? Iron in Sub-Saharan Africa" by Stanley B. Alpern, 2005
Regards,
Ed