I follow everything you say, with just one question. I agree gold and silver will fill the role, but there's the danger of counterfeit. How does that farmer know how pure that gold is? That silver bar? That jewelry? That's why I'm thinking some current 1 oz silver bullion coins, easily identifiable, are best if the monetary system collapses.
Isn't one characteristic of anything to be used as money an agreed upon and easily verifiable value?