40 Réis - João V counterstamped 20 Réis

Portugal's chronic copper shortage in the early eighteenth century forced the crown into an awkward fiscal maneuver: rather than strike entirely new coinage, existing 20 Réis pieces were counterstamped and revalued upward to double their face value. The decree authorizing this practice under João V effectively created money from money already in circulation, a stopgap that sidestepped the cost of full reminting while still expanding the nominal copper supply.

The counterstamp program ran across two decades, which means the host coins vary considerably in their original condition and date of striking. Authentication hinges entirely on the counterstamp itself — poorly applied punches and outright forgeries were documented even in contemporary records.