The mint at Mexico City was the first to strike coins for the Spain in the New World. It started in 1536 with some round and very well-executed issues under Charles-Joanna that are technically not known as cobs, and then it changed to the more familiar shield-type design in the late 1500s. This Mexican shield-type design was known around the world as a reliable coin, a true universal currency, the "piece of eight" that was referred to in nearly every major commerce area in its time (1600s and 1700s).

In 1732-1734 the shield-type cob was finally phased out and eventually replaced (after an experimental, machine-struck but hand-cut "klippe" type) by the even more-famous machine-made "pillar dollars."