Real Branco - João I Porto mint

João I's reign coincided with the opening of Portugal's Atlantic expansion — Ceuta fell to Portuguese forces in 1415, the same year this emission began. Funding that campaign, and the military apparatus it required, placed considerable strain on the royal treasury and directly influenced the debased silver content that defines billon coinage of this period.

The Porto mint's output for this type is notably scarcer than Lisbon's, a persistent pattern across João I's reign reflecting the northern facility's more limited production capacity.