240 Réis - João IV Countermarked 4 Reales

In 1663, the Portuguese crown authorized a mass countermarking campaign to address a chronic shortage of large silver denominations in Brazil. Spanish colonial 4 Reales pieces — already circulating informally — were officially crowned and revalued to 240 Réis, giving them legal tender status under João IV's authority despite João IV having died in 1656. The countermark was applied posthumously in his name, a bureaucratic anomaly that reflects how slowly royal edicts moved across the Atlantic.

Genuine countermarks are notoriously easy to fake. Period forgeries exist, and the authentication of the punch itself remains the primary challenge with this type.