The Bureau of Engraving and Printing says it makes mistakes like this "very rarely," but there are those who would like to see it happen more often.

A batch of misprinted $20 bills began popping out of an automatic teller machine at a Wells Fargo branch bank in Palo Alto, Calif., over the weekend. They could be worth as much as $1,000 each.

The faulty bills came to the attention of bank officials Monday when one of their customers came huffing back from a department store that refused to honor them.

Bank officials being bank officials, they doubted at first that the money could have come from their esteemed premises.

"My first reaction was that they were counterfeit," Wells Fargo's Palo Alto operations officer, Gary Lichau, told local reporters. "Then we looked in the machine."

Eight hundred dollars worth of misprinted twenties were still sitting in the money cartridge. The seal of the San Francisco Federal Reserve Bank and several serial numbers were missing. The bills were apparently part of a packet of 50 that had been stacked into the machine after somehow escaping part of a third and final run through the printing presses in Washington.

Bank officials being bank officials, the people at Wells Fargo insisted on a strait-laced, face-value exchange. As a result, the first customer, who came back with two twenties from the department store, walked out with only two everyday twenties in their place.

Phil and Julie Spickler weren't buying that kind of a trade. They'd withdrawn five of the rare bills without realizing it. They discovered what they had when a restaurant cashier told them there was "something wrong" with their money.

Bank spokesman Dale Walwark said the Spicklers wanted "another $100 instead of just exchanging the bills." Wells Fargo refused. The Spicklers walked out.

"We're either in the bricks or we're out $200," Phil Spickler was quoted as telling the Peninsula (Calif.) Times-Tribune where he took his story.

Numismatists indicated that he's "in the bricks." The bills could be worth $150 to $200 each if just the Reserve Bank seal is missing and as much as $1,000 if there are other errors, one expert told the Associated Press.

Wells Fargo officials figured that only three of the misprinted bills have yet to be accounted for. They said they know of no other bank or branch that got the valuable misfits.

"It's the first time it's happened to us," said one Wells Fargo official. He said the bills they retrieved are all being dutifully returned to the Fed in San Francisco.

In Washington, however, Bureau of Engraving officials acknowledge that there are almost certainly a few more floating out there somewhere.

The bureau solemnly announced that its Office of Security is "investigating" in an effort to determine just how many of the twenties might have escaped the government's clutches.

"They're all corner examined," said Larry Rulofs, assistant director for operations, in suggesting how the mistakes might have gone unnoticed. "You take a stack of them and rifle through at the corners."

But he wasn't sanguine about the prospects of a huge treasure trove still waiting to be discovered. "The likelihood of a lot of them getting through is really poor," he said.

Too bad. Government blunders like this ought to be planned.