100 Réis - João IV Countermarked 80 Réis

João IV died in 1656, leaving Portugal mid-war with Spain and its colonial treasury chronically short of small silver. The countermark program of 1663 — applied under the regency preceding Afonso VI's full assumption of power — was a fiscal stopgap: existing 100 Réis pieces were officially revalued downward to 80 Réis to discourage silver export and align circulating coinage with revised monetary ordinances. Brazil, as the crown's primary silver-processing colony, received these countermarked pieces as legal instruments of exchange rather than newly minted coin.

The applied countermark itself is the authenticating detail collectors must scrutinize — weak or doubled strikes are common, and outright forgeries of the punch exist.