A privy seal was in use during the reign of King John. From c. 1230 - during Henry Ill's reign - it became a permanent feature of royal administration, being used to authenticate letters less formal than those issued by the *chancery. It was usually kept by the controller of the *king's wardrobe until 1313, when the post of keeper of the privy seal was created. By this time the keeper was an important officer of state and the office went out of court. Acquiring further importance, the privy seal was replaced for more secret purposes by that of the *signet. The privy seal ranked between the *great seal and the signet; it was known sometimes as a secretum, i.e. something separate, kept apart and thus secret. The office was abolished in 1884. -
Dictionary of Medieval Terms and Phrases. Christopher Coredon with Ann Williams.