That regional Federal Reserve Bank keeps a record that identifies the purchasing bank. And the purchaser knows how it disposed of the bills. When they are found all together, it means that the bank that bought the bills did not feed them out from the teller window or the cash machine, but delivered them to a single customer.

And the bank knows who that customer was. Between, say, Philadelphia and Iraq, there is no doubt a chain, perhaps involving banks in the Cayman or Channel Islands, in Abu Dhabi or Dubai. Still, each bank in the chain can give the name of the customer to which it gave these bills.

Although Saddam Hussein's government had many sanctions against it, it may well be that no laws were broken in the passage of the Federal Reserve notes from the mint to Tikrit. But it would be interesting to know which banks were collaborators in getting that cash to the tyrant of Iraq.

Unfortunately, the search for these witting or unwitting collaborators cannot even get started, because the Federal Reserve Board will not permit regional banks to reveal the identity of the purchasers of large blocks of United States currency. There is no law that prohibits such disclosure; it's simply a Fed policy. Yet in this age of payroll services and electronic payments, there are few legitimate uses outside the banking system for very large orders of hundred-dollar bills.

The Fed has always resisted placing American banks under obligation to reveal skulduggery, whether it involves drug smuggling, commercial fraud, terrorism or other international conspiracy. Banks are not, the Fed insists, law enforcement agencies. It may be that the F.B.I. has access to the Fed's records -- a spokesman for the Fed, after checking with the main office, would not say yea or nay -- but it is not clear that the F.B.I. has authority to continue such searches beyond American borders.