Evaluation Of Foreign Currency Information

If you want to know current exchange rates for currencies, there are plenty of websites around. xe.com is perhaps the most famous.

The problem, however, is you really need to know a bit about the currencies before just buying them. Some countries may have reformed their currency, but confusingly kept the same currency name. For example, in 2005 Turkey slashed six zeroes from their currency: 1,000,000 old lira became 1 "new lira". Then in 2008, they renamed the "new lira" back to plain old lira again. So if you find a 50,000 Turkish lira banknote, looking it up on xe.com won't tell you accurate information.

Wikipedia is a good quick source of information for national currencies; they'll tell you which countries have had currency reforms, and which (if any) of the banknotes from older currencies might still be valid legal tender or exchangeable and which have been cancelled. Old pre-euro French francs, for example, are now worthless. But old pre-euro German deutschemarks can still be redeemed and exchanged for euros.

Coins generally aren't accepted by the moneychangers; nobody likes dealing in foreign small change. But current paper money is easily exchangeable. So it's reasonable to assume that any banknotes sitting around in a dealer's banknote box are not the kind you can readily exchange for US dollars, and probably also not the kind you can simply take and spend in their country of origin.