Tostão – João III 3rd type, Lisboa mint

The tostão denomination was introduced under Manuel I and became the workhorse of Portuguese Atlantic trade, circulating from Brazil to the Estado da India alongside cruzados and vinténs. João III's third type at Lisbon represents the final years of a reign defined by the consolidation of Portuguese India and the enormous fiscal strain of maintaining simultaneous commercial and military operations across three continents. By the mid-1550s, the crown was increasingly debasing subsidiary silver while preserving the higher denominations — the tostão's .9166 fineness held, but pressures on the Lisbon mint were considerable.

Gomes distinguishes three varieties within this type, J3 137 through 139, differentiated primarily by die details rather than weight or fineness standards.