CARLOS III

In Guatemala, onzas were first minted featuring a local bust (1761), and later the portrait of the king known as the Cara de Rata “Rat Face”, a work by Tomás Francisco Prieto, until the monetary reform of 1772. This portrait would go on to be widely adopted across the American mints (with the exception of Popayán), particularly from 1762 onward. Guatemalan coins from this period are extremely rare; the issues of 1765, 1768, and 1770 each present subtle variations in the obverse die, giving rise to what may be referred to as the "Guatemalan Rat Face" portrait. They are also distinctive for lacking an assayer’s mark. In particular, the 1768 onza, which features a sharply defined and finely executed portrait, is known today from fewer than ten surviving examples.