25 Céntimos Almadén

Almadén sits atop one of the world's richest mercury deposits, and its municipal council issued this emergency fractional note during the Spanish Civil War as part of the wave of local billetes de necesidad that flooded Republican-held territory when coinage disappeared from circulation. The Consejo Municipal, like hundreds of similar bodies across Spain in 1937, essentially printed its own small change out of necessity — the central Republican government had neither the logistics nor the material to keep small denominations flowing to isolated towns.

The official stamp served as the primary authentication, a common approach for these improvised emissions where engraved security printing was simply not available.