The seal first appeared in its developed form in England during Edward the Confessor's reign. The great seal was double-sided (unlike other English royal seals) and usually showed the monarch seated, as well as the royal insignia. Henry I's showed him on the obverse seated on the throne with orb and sword, while on the reverse he was mounted with sword and shield as duke of Normandy (dux Normannorum). In time it was augmented by other, smaller seals as the central administration expanded, then by the *privy seal, the keeper of which was a minister of state. Literal possession of the seal conferred immense power on its bearer; it gave and affirmed authority of sovereign and state. -
Dictionary of Medieval Terms and Phrases. Christopher Coredon with Ann Williams.