This was the flag captured by French troops in 1898 when they defeated Samory Touré, ruler of the Wassoulou Empire, and annexed his state into colonial France. 
Source: 

  Lux-Wurm, P. C., &amp; Zaragoza, Martha. (2001). Les drapeaux de l’islam : de Mahomet à nos jours. Buchet-Chastel. P.113
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