[Michele]

Having some commodity money, or representative money covered by commodities, has been common throughout of history - yet the preference seems clear for materials and items that don't spoil that easily. Metals, of course. But also salt, stone, wampums, arrow heads, beaver pelts. Tobacco was the commodity covering some scrips, but it's easier to preserve than grain. And, finally, there were systems in which the representative money was covered by rice or barley - but not necessarily the rice or barley of this year in this small place. On the one hand, the latter variation introduces, in a certain sense, commodity futures... but on the other hand, it protects you from a fire destroying this year's harvest in this one village's granary.

If the trend throughout history has been away from grain-based local currencies, I suspect that there must be good reasons for which the alternative is preferable - so we can't really railroad players into accepting the grain, or the grain-covered scrip.