In his dark blue pinstripe suit, light blue shirt and red tie, Nabil Feidy could easily pass for a prosperous Wall Street banker, perhaps a specialist in the exotic world of the international currency market.

Feidy, 28, is both banker and currency trader, but with a special Middle Eastern flavor. Operating from a one-room, storefront office equipped with the essential tools of his business -- an automatic currency counter, a calculator and a telephone -- Feidy is a thoroughly modern incarnation of an ancient Middle East institution, the Arab money-changer.

Feidy and a dozen other licensed money-changers whose storefront offices line Saladin Street in East Jerusalem are also the target of a new Israeli government crackdown against the flourishing currency black market in the country.

Beginning Sunday, according to a government edict, licensed money-changers like Feidy are to halt all trading in U.S. dollars -- the bulk of their business -- but can continue to buy and sell Jordanian dinars, which are still legal tender in East Jerusalem and the Israeli-occupied West Bank.

The money-changers were originally licensed by Jordan when it controlled East Jerusalem and the West Bank, and they have been allowed to continue to operate by the Israelis since Israel captured the territory in 1967. They serve an important function because the Jordanian dinar, which is not accepted by Israeli banks, is still widely used in the West Bank.

There are, in addition to the licensed money-changers, at least two dozen other money-changers in East Jerusalem who lack permits to do business. They are to close their operations entirely by next week, according to the Justice Ministry order.

It is the U.S. dollar, not the Jordanian dinar, that fuels the legal East Jerusalem currency market, and attempts to close down legal trading in dollars, it was widely said here, would have predictable results.

"The black market will boom," Feidy said with the assurance of a man who knows human nature as well as he does the daily value of the dollar against other currencies.

"They tried to do the same thing in 1976," he said. "They used to bust us, take us to the police headquarters in the Russian Compound. It didn't work."

It is not clear how serious the promised government crackdown against the Arab money-changers, and against the booming illegal street corner currency black market in Tel Aviv, is going to be. But on Saladin Street this week, there was every expectation that, government edict or not, it will still be possible to buy and sell dollars here after the new rules take effect.

The transactions may just be a little more complicated, perhaps with a tinge of excitement not normally associated with banking, and possibly even more lucrative.

"Come back next week and you will get 700 shekels for $1," a merchant at the City Grocery said with a laugh. Last week's rate for $1 in East Jerusalem was 580 shekels, compared to the official bank rate of 538 shekels to $1.

The government order banning trading in all foreign currencies except Jordanian dinars was the latest step in an increasingly desperate attempt to salvage what is left of Israel's national currency, the shekel. One measure of the shekel's precarious state of health was an announcement a week ago by Finance Minister Yitzhak Modai of plans to introduce a new currency, the "new shekel," largely because major transactions based on the old shekel involve such huge numbers that they are straining the capacity of bank computers to keep track of them.

But this step and earlier measures such as the imposition of tight new restrictions on the amount of foreign currency Israelis can take abroad may be too little and too late. For one thing, it is acknowledged even in the government that attempts to prevent Israelis from hoarding dollars, a severe drain on the country's foreign currency reserves, deal with only the symptoms, and not the causes, of Israel's economic malaise.

Israelis want dollars because they perceive the shekel to be increasingly worthless. Thousands of private cash transactions are carried out each day in dollars. Since the government agreed to a three-month wage and price freeze earlier this month, the Bank of Israel has slowed the daily devaluation of the shekel.

Still, the shekel is never worth as much today as it was yesterday, and there is a fear of a massive price explosion when the freeze expires in February. Dollars are the safest haven in the meantime.

There is also considerable skepticism about the likely effectiveness of the announced black market crackdown. There were predictions from money-changers that a serious attempt to run them out of business would drive up the cost of the dollar to 50 percent over the bank rate, instead of the roughly 10 percent premium now offered in East Jerusalem.

As in any financial center in the world, currency values fluctuate daily on Saladin Street. The dollar always sells for more than the Bank of Israel rate, with the premium largely determined by the Israeli public's hunger for dollars.

The daily rate, Feidy said, is also affected by the fluctuations in the value of the dollar against the Jordanian dinar. Of course, in the fractured world of the Middle East it is not possible to pick up a telephone in Jerusalem and call Amman for current currency trading quotations.

"We have a lot of ways to get the information," Feidy said, among them the daily traffic from Jordan that enters Israel across the Allenby Bridge.

With the detached judgment of a seasoned trader, Feidy noted that the announcement of the black market crackdown was made with great fanfare, and that the police officials who served papers on him and other money-changers last Sunday were accompanied by hordes of Israeli journalists and television crews. He calculated that the government's real purpose was psychological, an attempt to frighten the Israeli public away from Saladin Street and other centers of free market currency trading.

But, he said, "They can't control it. People called me this morning. Everybody wants dollars. It doesn't change."