The snake in the tunnel was a system of European monetary cooperation in the 1970s which aimed at limiting fluctuations between different European currencies. It was the first attempt at European monetary cooperation. It attempted to create a single currency band for the European Economic Community (EEC), essentially pegging all the EEC currencies to one another.
The tunnel collapsed in 1973 when the US dollar floated freely. The snake proved unsustainable, with several currencies leaving and in some cases rejoining; the French franc left in 1974, rejoined, and left again in 1976 despite appreciating against the US dollar. By 1977, it had become a Deutsche Mark zone with just the Belgian and Luxembourg franc, the Dutch guilder and the Danish krone tracking it. The Werner plan was abandoned.[1] The European Monetary System followed the "snake" as a system for monetary coordination in the EEC.