25 Céntimos Villanueva de la Serena

Villanueva de la Serena, a town in Extremadura, sat in Republican-held territory during the early phase of the Civil War and issued its own emergency fractional currency when the Republic's small-denomination coinage effectively vanished from circulation — hoarded, melted, or simply unable to keep pace with wartime disruption. These municipal notes, known collectively as billetes locales de necesidad, were produced by hundreds of Spanish towns between 1936 and 1938, most with rudimentary printing and minimal anti-counterfeiting provisions.

The official stamp is the only security feature — which tells you everything about how quickly and informally these were produced.