4 Pesos Tesoro Nacional - Black type

Paraguay's Tesoro Nacional notes from this period were issued under conditions of near-total economic isolation. The War of the Triple Alliance (1864–1870) severed international trade and made access to foreign printing houses impossible, forcing the government to produce currency domestically in Asunción — a significant constraint that shows in the execution. State-printed wartime notes from landlocked, blockaded nations rarely achieve the engraving standards of European presses, and this series is no exception.

The watermark is an unusual security feature for a domestically produced wartime issue and suggests at least some pre-war paper stock was still being drawn down during printing. By the war's end, Paraguay had lost an estimated 60–70% of its population — the monetary system effectively collapsed with the state that issued these notes.