In 1865, the four sovereign states of Belgium, France, Italy and Switzerland - Greece joined a little later - set up the Latin Monetary Union. The union covered only coinage, and had no common central bank. It was originally constructed as a forerunner of a political union — which was never established, though.
The founding treaty was open to interpretation in several respects, and that leeway was extensively exploited. Overall, commitment to the treaty was weak. One country was able to finance its public deficit by printing - or rather minting - money. What made those altogether rather heterogeneous countries stick together for more than 60 years was basically the need to tap the French capital market.