How cacao beans were used in some Mesoamerican markets, and why their role varied across societies and periods.
In some pre-Columbian and colonial-era Mesoamerican markets, cacao beans were used as a small medium of exchange. The Smithsonian's chocolate overview discusses cacao's role; that evidence should not be read as a single currency system shared across all Mesoamerican societies and periods.
Chocolate as a Medium of Exchange
Cacao was both a valued crop and an ingredient for drinks. Because beans were countable and portable, they could be useful in exchange; a market price depended on the place, date and goods being traded. Any quoted rate should therefore be tied to a specific historical account, not presented as a universal price.
Its use as a commodity and as a medium of exchange overlapped, but cacao beans were not official coinage with a fixed value across the region.
Quality and Local Exchange
As with other commodities used in exchange, buyers had to agree on the quantity and condition of the beans. The surviving evidence does not support treating cacao as a uniform, centrally issued currency.
Copper Hoe-Money and Jade Objects
A separate example is the Smithsonian's Aztec copper hoe-money object. It is evidence for a metal exchange object, not evidence that jade axe-shaped pieces formed one standard currency with cacao beans. The uses of jade objects need to be established from their own archaeological and historical contexts.