Elmer--I can't explain how'd they do it other than by threats and fear. Mao famously said power flows from a barrel of a gun. If you boil it down, everything our government does is by force--a barrel of a gun. In other words, if you don't comply, you are badgered with threats and paper work. If you still don't comply they send some armed functionary to arrest you. Resist and you are shot.
But it's not like they'll show up at your door asking you to cough up your gold and silver. They can't know who has what. (Unlike those of us who own guns). It's more likely they'll saddle us with some gigantic 'windfall tax' if we decide to trade PM for paper. In that event, a black market will inevitably come into being.
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