It's a counterfeiter's dream. But at the Bureau of Engraving and Printing, where the nation's paper money is made, it's a nightmare.

The bureau has lost -- well, misplaced -- a metal plate used to print $100 bills. And while officials say the plate probably is useless to anybody who would like to fashion $100 bills in the basement, they are searching every nook and cranny to locate the 3-foot-square, 8-pound object.

"We suspect at this point that the plate in question is still in the bureau," said Ira Polikoff, a spokesman for the bureau, a division of the Treasury Department. "We think that it is nothing more than a clerical error."

The plate, which can print portraits of Benjamin Franklin and most other essential features on the fronts of $100 bills, 32 at a time, was not located in a routine inventory July 6. Because it was defective, the plate was supposed to have been destroyed.

Officials double-checked their inventory, called in the Secret Service to help and even sifted through bureau refuse at the Lorton landfill.

Polikoff said it is unlikely that someone walked out of the bureau with the plate, given its size and weight.

In any case, he said, the plate would be of limited benefit to a counterfeiter, both because of its defect and because it is designed to fit on special presses and is missing several important parts of an actual $100 bill. It probably has more value to collectors, and indeed, first word of the missing plate appeared in Coin World, a collector's publication.

Still, to the best of anybody's knowledge, the Bureau of Engraving and Printing has never lost one of its plates before, and bureau officials are eager to find this one. One possibility, Polikoff said, is that the serial number on the plate was marked down incorrectly during the inventory, causing it to be listed as missing when it is not.

Or, Polikoff said, "Perhaps somebody picked it up and moved it to someplace where it shouldn't have been."