2 Reales Osorno - Insurgent countermarked coinage

During the Mexican War of Independence, royalist silver coins were seized and counterstamped by insurgent forces operating out of Osorno — a guerrilla commander, José Francisco Osorno, who controlled territory in the Sierra de Puebla and needed a circulating currency his forces would accept. The countermark transformed a coin of the colonial crown into an instrument of rebellion without melting a single gram of silver.

Authenticating these is genuinely difficult. Contemporary forgeries of the countermark existed almost immediately, since acceptance depended on the stamp rather than the host coin.