4 Escudos - Carlos III bust of Carlos III, regular type

Carlos III's colonial gold coinage underwent a fundamental design shift in the 1770s when the "bust" portrait type replaced the older "macuquina" cob coinage across Spanish American mints. Santiago's adoption of the milled bust format was part of a Bourbon administrative drive to standardize and professionalize colonial currency — a project with as much to do with anti-counterfeiting and metropolitan control as with aesthetics. The Santiago mint had long been considered a secondary operation compared to Lima or Mexico City, and quality control was an ongoing concern for Madrid.

Dies for these issues were cut locally, which accounts for subtle portrait inconsistencies across the 1773–1788 run that specialists use to attribute individual strikes to specific assayers — the assayer's initials being the primary diagnostic point within the KM#33 type.