While Botswana has a long history of allowing Business Reply Mail, examples of this material with return addresses in Botswana is unknown. Business Reply Mail with allowed use in Botswana / Bechuanaland with a return address to South Africa is known, but is extremely scarce.
I wrote an article describing this service and its history in Botswana that appeared in this information that appeared in Forerunners, the Journal of the Philatelic Society of Greater Southern Africa, Issue #115, May-August 2026.