On July 11, 1960, under President Moise Tshombe (1919-1969), the State of Katanga declared its independence from the Republic of Congo-Léopoldville. Shortly after seceding, Katanga sought to introduce its own currency: the Katangese franc. Jean-Baptiste Kibwe (1924-2008), Katanga's Minister of Finance, eventually approached Belgian artist Claude Charlier (1930 -) and requested he design the breakaway state's 1 and 5 franc coins. Charlier, who first arrived in Belgian Congo in 1952 with the Belgian Armed Forces, settled in Elizabethville (now Lubumbashi) after two years of service. There, in what would eventually become the capital of Katanga, the Belgian established a name for himself as both an artist and a professor at the University of Elizabethville (now the University of Lubumbashi). Charlier accepted Kibwe's request, and produced paper designs for both sides of each coin, and three copper models for the common obverse. These were then submitted to President Tshombe, who approved of the designs. Through a representative of the English company Imperial Chemical Industries (ICI), contacts were eventually made with the mint in Birmingham, which agreed to strike the coins.
Note that at the time there were two mints in Birmingham: one known as the Birmingham Mint (ex Heaton & Sons), and King's Norton Metal Co., which had been part of ICI since 1926.
In an interview with Charlier, Belgian numismatist Leopold Verbist inquired about the design, pointing out that "bananas grow upward and form relatively straight clusters, not toward the bottom and tapering to a point". In response, Charlier explained that he needed to narrow the bottom in order to get the bunch of bananas in the "circle of the coin".
The coins entered limited circulation in 1961, but were withdrawn after Katanga's reintegration into Congo-Léopoldville in 1963. It seems that a significant part of the issue never made it to Africa, as most coins found on the market are in uncirculated state.
[Article] Claude Charlier, graveur van de munten van Katanga, by Leopold Verbist, 2007 (PDF, in Dutch)