Thebes was the main commercial centre in the duchy of Athens and the mint there began to produce copper coins not before 1240 and continued until at least 1287. In around 1280, the lords of Athens began to mint billion deniers in the style of the French royal denier of Tours (deniers tournois).
Metcalf, David Michael. Coinage of the Crusades and the Latin East in the Ashmolean Museum, Oxford. London: Royal Numismatic Society, 1995. Pages 271 - 272
Credit line
The Mildred King Memorial Collection. Gift of Colonel E.J. King, 1935