i've read that the sotho (basoto) tribes of south africa (lesotho is named after them) did indeed make these style axes, the zulu did not make their own axes, but traded with the sotho tribes for them, the zulu preferring theirs. i've also heard the zulu would be paid tribute in weapons from other tribes in the area, including iwisa as well as axes, etc.
axe should be arriving today, i'll check the haft. it may have been varnished by a previous UK owner...
i suspect the wood is suffering from some neglect & ageing. it ooks like the rust may have impregnated the wood near the head resulting in some staining.
i'll also get my brass & nylon brushes out & wash/brush off the active rust & give it a coat of ballistol...