You jest about the flickage, but in fact it's a pretty useful way of spotting your average forgery - it also works for certain European national ID cards. You should expect to hear a plasticky "thwunk" rather than a papery "click"... Dropping the card onto a hard surface such as a table produces a similar result. With more than a passing interest in forged documents I know what a genuine one is supposed to "sound" like, but I can understand the lay-person's reaction to this article. Perhaps the help line will play you a recording of various cards being flicked for comparison purposes?!