There are dozens of currencies claim to have achieved currency convertibility, including nearly ten have worldwide influence.

自称本币已实现可兑换的货币，有几十种，有影响的也有近十个。

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In an earlier phase of capitalism, Britain and the earlier European commercial powers (the Dutch Republic, Sweden) created central banks either to lend money to the government or to stabilise the convertibility of trading currencies into gold.

BBC: Central banks are part of the state