There are a ton of LED keyring lights out there, in just about every color, and aside from lighting up the doorway as we stumble home late at night, we haven't really seen any huge value to them. However, in a review of the Purple Photon Micro-Light II, the Gadgeteer points out a good reason why a purple LED comes in handy: it works as a quick and dirty counterfeit cash detector, since it can illuminate embedded fluorescent strips that are used in banknotes, checks and credit cards. That, and it also gives you a trippy blacklight effect, but we'd already figured out that one.
Gadgeteer reviews Purple Photon Micro-Light II
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