[Polybius]

If that is true (the point being questioned in this thread) the two currencies would circulate in different economies (domestic and international) and could conceivably be assigned different values by their respective markets. That mechansim - two different markets, not different years, - could devalue the domestic currency.

Actually, if there were any devaluation, it would devaluate the old currency that is now circulating overseas as that currency would be riskier to hold.

Consider the case of the "Hawaii Dollar":

This U.S. currency, with "Hawaii" printed on it, was issued during World War II for circulation in Hawaii. If the Japanese had ever captured the Hawaiian Islands, the U.S. Government could have immediately declared all "Hawaii dollars" to be worthless.

The old U.S. currency circulating overseas has now become the 2003 version of "Hawaii Dollars".

By demonitizing the old currency after a period when it can be exchanged only at banks, the U.S. Government can, at any time of it's choosing, convert the narco-traffiker's and terrorist's cash reserves of billions of U.S. dollars into souveniers that would be bought and sold in the "Obsolete Currency" category on eBay.

[Lonesome in Massachussets]

By demonitizing the old currency after a period when it can be exchanged only at banks, the U.S. Government can, at any time of it's choosing, convert the narco-traffiker's and terrorist's cash reserves of billions of U.S. dollars into souveniers...

What is money? It cannot breath life into the now-dead dreams of childhood. It cannot heal a broken heart nor repair the shattered portals of a broken home. I speak, of course, of Confederate money. - Joel Chandler Harris