1 Real - Philip IV

1652 is the year of the Santa Margarita and Nuestra Señora de Atocha disaster — but more consequentially for Potosí, it is the year the Spanish Crown discovered that the assayer Francisco de la Casa had been systematically debasing colonial silver for nearly a decade. The resulting scandal shuttered the mint entirely in mid-1652, with all assayers arrested and several executed. Coins struck in the months immediately before the closure carry the disgraced assayers' initials and were officially ordered recalled, though vast numbers remained in circulation.

The 1 Real cob from this mint and year sits at the center of that crisis.