Ok, lets say we go back currency based on metals. If that happened and I were China and Japan I would just call in my debts and demand to be paid in metals at the current rate set by the Fed.
Currency backed by metals is not realistic if other currencies are not backed by metals. Also there is too much debt on this planet to even consider backing up your currency into a metal. Don't forget that if you back up a currency with a metal there is a price tag attached to extraction, storage and eventual distribution of the metal when demanded.
Also all those people claiming that there will be a world currency are living in a fairy tale. Just look at Euro. So far it has only been 12 years since it went into the banking system and 8 years in circulation in the economy and it is already proven to be a painful experience for nations that are in trouble and are tied to the currency.
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