Complete History of the Planet Skaro

The Complete History of the Planet Skaro was maintained by the Thals, appearing as a series of plates which shown the orbit of their home planet of Skaro within the Skaro system. (PROSE: Dalek Combat Training Manual) In the time of the Thal-Dalek battle, the First Doctor observed that the Thals' records went back nearly half a million years. (TV: The Daleks)