Heh, the pre-1982 penny problem is solved with a cheap coin comparator !
I read an article about a guy that is hoarding Nickels because of the metal content -- as in ordering up tons of the things from the mint and storing in secured warehouses.
The idea wasn't so much that you'd use only coins as the "asset-backing" to the pool just that the chain would be backed by a specific metal/commodity and that the implied underlying exchange policy would be that you could demand the exchange/cash-out but that the transaction fee's would likely make it not worth the minting expense. Thus, its a promissory-note kind of instrument. And really, if you wanted to convert your CuBITs I'm sure someone would be happy to 'mint' out a heavy box of pennies + the shipping, insurance -- and the money maker "handling" charges for you
For that matter, why not use the 1 Yen coin? It's still 1g of 100% aluminum afaik??