50 Francs

The Banque Nationale de Belgique was only a year old when this note entered circulation — the bank was founded in 1850, and the 50 Francs was among its earliest emissions. Léopold Wiener was primarily a medallist and engraver to the Belgian royal court, not a commercial banknote designer, which gives this issue an unusual sculptural quality in its intaglio work that later BNB notes largely abandoned in favor of more conventional security engraving.

Pick 4 is genuinely rare at this date. Early Belgian notes suffered heavy attrition through redemption and destruction, and the 1850s issues are among the most seldom encountered in any condition.