You can protect yourself using forward foreign exchange contracts and currency options.
In September 1987, the exchange became the first to open night trading in foreign currency options.
Executives at other financial institutions that also trade currency options have found the bank's explanation puzzling.
The central bank has never used Banesto to sell currency options.
A better reason to look at the Philadelphia exchange's site is to get information about currency options, which are traded there.
Through mid-July, 51,225 currency options traded daily on average, up from 42,865 in 1991.
Still, it is in currency options that the exchange will break its next bit of ground.
Since 1982, foreign currency options have turned into much more than a Philadelphia story.
"Before we started, there were not many banks who were doing currency options," he said.
VW officials said its computers had been used to trade in foreign currency options.
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