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<p>[QUOTE=&quot;Numbers, post: 338462, member: 11668&quot;]What nobody&#039;s pointed out yet is that the backs of U.S. currency are actually printed with two different green inks.&nbsp; They look identical under normal light, but one of them disappears under infrared light.&nbsp; The special green ink is used for a vertical strip in a different location on each denomination, making it easy for an infrared scanner to identify the genuineness and denomination of each bill.&nbsp; Some vending machine bill acceptors check this, as do the little hand-held scanners that the blind can use to keep track of which bill is which.</p><p><br /></p><p>Anyway, this bill seems to be the result of a press running out of one type of green ink but not the other.&nbsp; So you see an underinking error, but it&#039;s restricted to that one narrow strip of the bill where the special ink should have been.&nbsp; Nifty error note; should be worth a bit.</p><p><br /></p><p>Oh, and in response to the other commentors: the &quot;counterfeit detection&quot; pens are a joke.&nbsp; They should not be relied upon for anything ever.&nbsp; Most good-quality cotton bond paper will pass the pen test; on the other hand, a genuine bill that&#039;s been through a laundry cycle will often fail it.&nbsp; The pens will catch fake bills that some kid laser-printed on ordinary computer paper, but that&#039;s about it.&nbsp; And the pen marks do not fade away completely, though they do lighten over time, so the pens should *definitely* never be used to authenticate currency that might be collectible.[/QUOTE]</p><p><br /></p>

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