By way of example of the variable nature of a document, in this case, FDS was asked to examine a large collection of stolen mammalian skulls that originally contained handwritten codes identifying which species they belonged to.  The thief attempted to physically erase the museum's identification codes so that he could start up his own private collection.  After the skulls were recovered by police, FDS was instructed to try and restore the original erased entries so that the museum could return the skulls to their appropriate sections.  We examined each skull under high magnification using various photo-analytical techniques.  The majority of the original codes were deciphered using these techniques and the museum was able to return most of the skulls to the appropriate collections.