Counterfeit passport number. Image 1 of 2. Output from a scan by a video spectral comparator. The letter 'B' appears normal in visible light. The spectral comparator allows changes to the viewing light used, which can reveal fake documents. Ink has here been added to a letter 'E' to turn it into the letter 'B'. This deception is revealed under light of a different wavelength, and so the genuine letter is seen in image T980/214.