Under a currency board arrangement, the central bank guarantees the redemption of all notes in circulation at a set exchange rate to the dollar or another foreign currency or basket of currencies.

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While the southern coast of Spain was once believed to have the highest concentration of 500-euro notes in circulation, the distinctive purple bill has become more like the unicorn of Europe because they are rarely seen.

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More than 30 billion rupee notes are in circulation, a total growing by 11% a year.

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Critics might fret that the recent slowdown in the growth in Japan's monetary base (banks' reserves at the central bank plus notes and coins in circulation) suggests that the Bank of Japan has tightened policy.

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This was inevitable: airlines have been issuing so many miles (for spending on the ground as well as in the air) that the total stock is worth more than all the dollar notes and coins in circulation.

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The Irish punt will continue to exist in dual circulation with the new notes and coins until 9 February.

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Minting the coins is under way, as a far greater number of coins than notes will be needed: some 76 billion coins are in circulation in the euro countries.

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Spokeswoman Elvira Swanson notes that the company has more than 1.8 billion cards in circulation and is active in more than 200 countries around the world.

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The colourful new notes could end up just like the tattered old Sudanese pounds already in circulation, changing hands at wildly different rates from village to village.

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The unfit notes are destroyed and the notes deemed fit for re-circulation are added back into Reserve Bank inventories to be paid out to banks in filling future orders.

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