Jetton, Anglo-Gallic.

Brass reckoning counter, or jetton

Anglo-Gallic type, 14th-15th century

Jettons were intended to be used in computation, in the European equivalent of the abacus. They were laid out in rows on a checker-board - hence the modern 'Exchequer' - and were used in almost all arithmetic in the later Middle Ages and into the 17th century. For most of this time Roman numerals were still in use, which were difficult to use in written calculations. At first, actual coins seem to have been used, until the idea occurred of producing cheaper counters in base metal. The designs of many jettons are based on the designs of coins.