More info on wire wrapping of Zulu weaponry:
https://www.vikingsword.com/vb/showthread.php?t=15402
Note the section there on 'tribute' weapons.
Conquered tribes were the main suppliers of Zulu weapons, makes it harder to pin down exactly where they were made. It also accounts for variations in wood used, variations of head shapes. Note the flat area on the lower part of the head, below. it's actually dished slightly. I gather that to prevent cracking they would stand the iwisa in a corner, dished area up, and put a dollop of fat in it which would slowly melt into the wood. I've seen a few that did crack, probably since the weapon was acquired by a European who did not carry out the process. (Hint - rub yours with a good furniture oil on occasion)
Another one of mine - a favourite - illustrating the offset head mentioned above, sadly no wire work: