reunion of these countries might still be feasible based on the findings of economic convergence. List of currency unions Existing Note: Every customs and monetary union and economic and monetary union also has a currency union. is theoretically in a currency union with four blocs as the South African rand, Botswana pula, British pound and US dollar freely circulate. The US Dollar was, until 2016, official tender. Additionally, the autonomous and dependent territories, such as some of the EU member state special territories, are sometimes treated as separate customs territory from their mainland state or have varying arrangements of formal or de facto customs union, common market and currency union (or combinations thereof) with the mainland and in regards to third countries through the trade pacts signed by the mainland state. Currency union in Europe The European currency union is a part of the Economic and Monetary Union of the European Union (EMU). EMU was formed during the second half of the 20th century after historic agreements, such as Treaty of Paris (1951), Maastricht Treaty (1992). In 2002, the euro, a single European currency, was adopted by 12 member states. Currently, the Eurozone has 20 member states. The other members of the European Union are required to adopt the euro as their currency (except for Denmark, which has been given the right to opt out), but there has not been a specific date set. The main independent institution responsible for stability of the euro is the European Central Bank (ECB). Together with 15 national banks it forms the European System of Central Banks. The Governing Board consists of the Executive Committee of the ECB and the governors of individual national banks, and determines the monetary policy, as well as short-term monetary objectives, key interest rates and the extent of monetary reserves. Planned Disbanded between Bahrain and Abu Dhabi using the Bahraini dinar between Bahrain, Kuwait, Oman, Qatar and the Trucial States, using the Gulf rupee from 1959 until 1966 between Aden, , Bahrain, Kenya, Kuwait, Oman, Qatar, British Somaliland, the Trucial States, Uganda, Zanzibar and British India (later independent India) using the Indian rupee between Belgium and the Grand-Duchy of Luxemburg (Belgium-Luxembourg Economic Union) using the Belgian/Luxembourgish franc from 1921 to the Euro between British India and the Straits Settlements (1837–1867) using the Indian rupee between Czech Republic and Slovakia (briefly from January 1, 1993 to February 8, 1993) using