Luc, you could be right, probably a copy from a neighbouring tribe. i also believe it's a cult knife.
The blade was probably, at some time, 'married' to this bigger handle. Although, in my opinion, it has been with this blade for quite some time.
The knife blade is thick (about 1 cm at the base of the blade). I haven't cleaned it and i'm not planning to do so. The coloured blade appeals to me.
Here's a painted knife I found in one of my books. According to the author from the Ngul and/or Yanzi-tribe. This one has spots painted on it.