The Seal of Rassilon was a symbol of the Time Lords. It was a symbol of power, utilised by Rassilon during the war against the Great Vampires and against the Old Ones. (EDA: Interference: Book Two)
The symbol was also taken up by other cultures whom the Time Lords visited early in their explorations of space and time, such as the inhabitants of Voga. (DW: Revenge of the Cybermen, NA: Cat's Cradle: Time's Crucible)
The Seal was used as a symbol of identification, and something akin to deep reverence. (DW: The Five Doctors, Doctor Who: The TV Movie)
