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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Holders of precious metals or other major tradable (fungible) assets worldwide need to monitor the foreign exchange rate of the currency in which their asset is held.

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And in some cases a bank decides on its own to hold on to a transfer in the hope of getting a better foreign-exchange rate for the customer the following day, or in order to batch it with other transfers and so lower its costs.

ECONOMIST: Banking