The USD, to my knowledge, has never been "revalued"... that is, reissued at greater value. In the late 80s, I lived for a time in then-Yugoslavia, back before the Balkan war (pre-EU) -- the Yugoslav economy was tanking, and price inflation was going nuts. Twice a day, stores would look at the exchange rate of the Yugo Dinar to the German Deutschmark (considered the standard of stability), and change (inevitably increasing) prices on all items accordingly. Extremely inefficient, but then, what can you expect in a communist regime?
A carton of milk could be thousands of Dinars. It was a hectic time. While I was there, the government announced that starting on the next Monday, there would be issued a "new Dinar", valued at ten times the exchange rate of the old Dinar to the Deutschmark. Being largely a cash economy, all citizens were required to hit the banks, turn in their old currency, and receive the equivalent in the new currency. Right pretty bills BTW, as I recall.
The effect was more psychological than practical, of course -- things retained their intrinsic value, it was just that the numbers were smaller. This was supposed to make everyone feel better about the fact that their country was disintegrating. It didn't work, and a couple years later, Slovenia and Croatia seceded from Yugoslavia, and the Balkan War had begun.
I've halfway been expecting the US to pull a similar stunt one of these days. But the dollar will no doubt implode altogether before our beloved bureaucrats get around to such creative (as in, pointless) thinking.
