Not long after Paul Smith's furniture and curiosity shop opened on Albemarle Street in London's Mayfair about a year and a half ago, I went in and was immediately drawn to a large, colourful and undeniably African flag that hung on the wall. I would have bought it if it wasn't something like $3000. Even so, I made a note of what it was: a Fante Asafo flag.
The Fante people are mainly gathered in Ghana, and the Asafo are local "companies" of men. They serve several purposes, from celebrating festivals, inaugurating chiefs and defending their town or village. Loosely organised along millitary lines, each company has its own distinctive flag that, until the late 1950s, had an approximation of the British Union flag in one corner. They're beautiful to look at and the images tell stories unique to the area from which they come.
Boston's Hamill Gallery of African art usually has good selection, that aren't too expensive.