Seems nonsensical. Detectors of money containing trace amounts of magnetized metals would have real trouble with other magnetized metal going by, and they're not going to stop people at airports to *If* this were true (which I strongly doubt at the 99% confidence level), it would work not with metal detection but with detection of a tuned circuit which would oscillate at a harmonic if you broadcast a certain frequency at it. There are several patents for such circuits - they're used in little strips that are slid down the spine of library books for instance. It could only ever be a gross detection measure - I guess it could be made to catch sums considerably over the 10,000$ cash limit quite effectively. But the fact is, people can strip a bill down and *look* at these things for themselves. I seriously doubt any such technology would remain invisible to some lab hack who in an idle moment put it under his SEM for a quick peek. (*any* school that fabs its own ICs could do it trivially in seconds.) G