Four stamps from Botswana

Title: Four stamps from Botswana
Description: 1979 Four stamps celebrating the international year of the child, 1979. Botswana appears as Bophuthatswana. Stamps have textual material in English or Dutch. Value of each stamp ranges: 4c, 15c, 20c, and 25c. The 25c stamp features two humans walking with a donkey or mule, which appears to have significant burdens. Unknown source.

Might the story behind this stamp be MSA? It would only be a sign that Aesopic stories get around!
Date: 1979
Subject: The Miller, His Son, and Their Ass