In 1961, eight countries (the United Kingdom, France, West Germany, Switzerland, Italy, the United States, Belgium and the Netheriands) informally agreed to intervene in the London Gold Market to prevent pressure on the price of gold and avoid too much speculation by preventing the price from rising above $35-19,875. This was done by forming the Gold Pool. In 1967 at the time of U.K. devaluation, France, for reasons best known to herself, opted out. and there was considerable speculation. This led to a crisis in the Gold Market, the creation of a two-tier price system, and the abandonment of the Gold Pool.
Reference: The Penguin Business Dictionary, 3rd edt.