I just saw a letter to the editor in Business Week saying that most walk-through detectors sense only ferromagnetic objects, which is not a property of American coins. If this is the case, then why are we asked to remove all change (besides that we might leave it behind and decrease the budget deficit)?

Interesting aside, is that our paper money is ferromagnetic, so the walk-through detector could be set so that paper money could be sensed.

If the foregoing is true, then one could walk through a security point with a stainless steel sword without it being detected by the machine?