10 Francs – Grand Duchy of Luxembourg

In 1929, the Grand Duchy of Luxembourg was operating under a unique and complex monetary regime, a legacy of its economic union with Belgium established in the 1922 Belgium-Luxembourg Economic Union (BLEU). This agreement created a de facto currency union, though not a full monetary union. The legal tender in Luxembourg was the Luxembourg franc, which was pegged at par (1:1) to the Belgian franc. Belgian banknotes and coins circulated freely alongside Luxembourg's own issued coins and, from 1929, its first series of state-issued paper banknotes. However, the Belgian franc acted as the anchor and primary reserve currency, meaning Luxembourg's monetary policy was effectively set in Brussels.

The year 1929 itself was a pivotal moment, marked by Luxembourg's issuance of its first series of treasury notes (billets de trésorerie) in denominations of 50 and 100 francs. This was a significant step in asserting a more visible national monetary identity, though the system's fundamentals remained tied to Belgium. These notes were not issued by a central bank (as Luxembourg lacked one until 1998) but by the state treasury, guaranteed by the government and fully backed by holdings of Belgian francs and gold. This move reinforced the credibility of the Luxembourg franc within the parity system.

This arrangement provided crucial stability, especially as the global economy teetered on the brink of the Great Depression. By anchoring its currency to Belgium's, Luxembourg, a small and open economy, imported the monetary stability of its larger partner and facilitated seamless cross-border trade. However, the system also meant Luxembourg had to passively follow Belgian monetary decisions, sacrificing independent control over its interest rates and money supply. Thus, in 1929, Luxembourg's currency situation was one of dependent stability, a carefully managed compromise that supported its economic integration while taking a cautious step towards a distinct national monetary expression.