Gold standard
Gold species standard
Gold Bullion standard
Exchange control was introduced post world war I (huge currency printed) inflation, followed by depression ' turmoil in 1930-s
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BRETTON WOOD Conference initiative to create multilateral currency system held in 1944 ' led to IMF and IBRD. To start with fixed rates were introduced (vis-à-vis USD or Gold0. IMF to permit changes in valuations of currencies (almost automatic for changes upto 10%) ' to avoid sudden changes impacting others.
Ordinary Drawing Rights (ODR) was created to help countries with Balance of Payment problems. This was to avoid any sudden changes in valuation. Or sudden imposition of limits on forex payments by their traders due to shortage.
Bretton Woods under pressure ' spate of devaluations ' Franc in 1958 (14.9%), GBP in 1967, Franc again by 11.1% in late 60’s. The DM and Dutch Guilder were revalued in 1961 and DM again in 1969. The US faced huge BOP problem in 1958-60. All these led to a severe strain on fixed rate system..
In early 1970-s USA continued to face huge deficits (one reason was expenses on Vietnam war) including the problem of migration of capital to relatively higher interest earning economies in Europe. Few European countries allowed their countries to float while few others revalued their currencies. As a result the fixed rate or Gold backed USD system suffered and was not possible to continue.
USA devalued their currency in 1971 and again in 1973. In March 1973 many European countries suspended their obligations to the IMF (for limiting the range of fluctuations of their currencies) The BW system was officially replaced by Floating Rate system in 1976.
SDR was created in 1969 These are not credits but currency reserves in addition to then existing Gold and USD reserves. The quantum of SDR-s allocated was decided by IMF and was at par with ODR=-s. Initially the value of SDR was fixed in Gold but later changed to basket of 16 currencies...