1 Peso Fuerte Oficina de Cambios

The Oficina de Cambios — Paraguay's exchange office rather than a full central bank — issued this series as a stopgap instrument during a prolonged period of monetary instability following the Chaco boundary disputes and the country's chronic difficulty attracting foreign capital. ABNC printed the notes in New York, which was standard practice for Paraguay at the time; the country lacked any domestic printing infrastructure capable of producing secure currency.

Four distinct signature combinations are documented for P#138, reflecting successive administrations of the Oficina rather than separate print runs — the plates were not changed. Zubizarreta's signature appears on all four pairings as the constant counter-signatory.