Oldsmobile Kalahari mail - classical era carried covers

A cover from Kalk Bay, South Africa carried by Oldsmobile Expedition across the Kalahari Desert from Gobabis to Ghanzi cancelled by the special and extremely rare OLDSMOBILE / 23 Nov 1929 / KALAHARI MAIL.

Also a newspaper article on the mail. 

Only a handful of covers are recorded and this mail is therefore very scarce.