Cruzado 'R-P, 7 castles' - João III 3rd type, Porto mint

João III's monetary reforms of the 1530s produced several short-lived cruzado variants as the crown worked through successive adjustments to gold fineness and weight standards. This third-type issue from the Porto mint is among the briefest in the sequence — struck across a window of roughly one year before further revision superseded it. The Porto mint itself was a secondary operation, and its output for this type was substantially lower than Lisbon's, which accounts for the relative difficulty of locating well-attributed examples today.

The 'R-P' mintmark pairing and the seven-castle shield configuration are the identifying details that separate this from the second type at attribution.