480 Réis - João IV Countermark 'Crowned 480' over Spain-America 8 Reales

In 1643, the Portuguese crown faced a chronic shortage of large silver denominations following the 1640 restoration of independence from Spain. Rather than strike new coinage outright — the mints lacked the capacity — João IV ordered that circulating Spanish colonial 8 reales be countermarked and revalued at 480 réis for legal tender in Portugal. The host coins were typically cob-struck pieces from Mexico City, Potosí, or Lima, meaning the planchet quality beneath the punch varies enormously.

The countermark itself is the authentication; the host coin's origin is incidental.