The stamps to complete my 1931 set of South West Africa’s* first definitive stamps arrived in my mailbox today, and I promptly added them into my album.
*Namibia, since 1990. Namibia’s history spans from the arrival of hunter-gatherers like the San and the Bantu-speaking peoples to European colonialism and finally, independence.
Key periods include it as a German colony (1884-1915), a South African mandate (1915-1990), and the struggle for independence during that time, culminating in the nation’s independence on March 21, 1990.
[Source: Google Search Labs | AI Overview]

I have a mint 1½d pair coming, but the used ones that I have now with OTJIEWARONGO and GROOTFONTEIN postmarks are cool, too.
What’s unusual with this set is that the country name is in a different font for each denomination. Usually, the lettering for the country name is identical for all the stamps in a definitive set.
The 20 shilling stamp denomination at the very end of the set is an extremely high value and must have been intended for very heavy or very large parcels. (20 shillings translates to a modern currency value at least 10x than the highest denominated modern stamps!).
Furthermore: The “Okuwahakan Falls” depicted on the 1931 20-shilling stamp of South West Africa is something of a mystery. Despite its prominent appearance on the stamp, there is no well-documented waterfall in present-day Namibia known by this name, either historically or currently.
Chat GPT says it is possibly a former or obscure name for a known waterfall:
One candidate is Ruacana Falls on the Kunene River (the border with Angola).
Another is Epupa Falls, further downstream on the Kunene. Both are among Namibia’s only notable large waterfalls.
It is speculative, but “Okuwahakan” could be an old or alternate indigenous name for one of these falls.