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Counterfeiters stamp images onto hot foil to simulate the metal security
strips embedded in bank notes, the security company De La Rue of Basingstoke
admits in GB 2347646. A new kind of security strip should spoil their game. The
strip is made from polyester, with a hologram on one side and a text message
printed on the other. The text is coated with a pigment that becomes transparent
when heated above 35 °C. When the bank note is viewed at low temperatures,
only the coating is visible because the pigment obscures the text. When the note
is warmed, the coating…