1 Franc – France

In 1866, France operated under a bimetallic monetary system, established by the Latin Monetary Union (LMU) treaty of 1865. This agreement, which included Belgium, Switzerland, Italy, and later Greece, standardized coinage by fixing the gold-to-silver ratio at 1:15.5. The goal was to create a stable, uniform currency zone that would facilitate trade and economic integration across participating nations. French coins like the gold Napoléon and the silver 5-franc piece were legal tender throughout the union, representing a significant step toward European monetary cooperation.

However, this system faced profound structural pressures. The fixed mint ratio did not reflect the fluctuating market values of the metals, particularly as new silver discoveries in the Americas increased its supply and drove its market price down. This created Gresham's Law in practice: cheaper silver flooded into the LMU mints to be coined at the artificially high rate, while gold coins were increasingly hoarded or exported. Consequently, France was effectively draining its gold reserves to support an overvalued silver currency, placing the entire bimetallic framework under severe strain.

The situation in 1866 was therefore one of precarious transition. While the LMU promised stability, the inherent flaws of bimetallism were becoming untenable. French monetary authorities, led by the Banque de France, were grappling with the practical reality that the system was evolving toward a gold standard de facto, even as the law upheld bimetallism de jure. This period set the stage for the eventual, though reluctant, shift of France and the LMU toward a gold-based system in the following decades, as the international monetary order began to coalesce around gold.