4 Reales - Charles III

Charles III's colonial minting operation at Potosí ran under chronic pressure — the cerro rico mines were past their peak productivity by the 1770s, and the transition from the old macuquina (cob) coinage to the new milled portrait coinage had already generated one of colonial Spanish America's great scandals. In 1649, assayers had been executed for debasing the silver; the memory of that episode shaped Potosí's reputation for the remainder of the colonial period.

KM#54 belongs to the milled series introduced after the reforms of Philip V, completed at Potosí later than at other mints. The local assayer's initials appearing on these pieces were a legal accountability measure — the named official bore personal liability for fineness.