that multiple commodity currencies can't coexist in a free market!
"A particularly important case of Gresham's Law was the perennial problem of the "standard." We saw that the free market established "parallel standards" of gold and silver, each freely fluctuating in relation to the other in accordance with market supplies and demands. But governments decided they would help out the market by stepping in to "simplify" matters."
If the Govt steps in and declares values of commodities then trouble ensue. The only thing markets do is discover trade values and it can't be messed with without nasty things happening when said market attempts to rediscover equilibrium.
~wobbles but doesn't fall down~