What does "signet" mean?

Signet: A seal; especially, in England, the seal used by the sovereign in sealing private letters and grants that pass by bill under the sign manual; -- called also privy signet. I had my father's signet in my purse. Shak. Signet ring, a ring containing a signet or private seal. -- Writer to the signet (Scots Law), a judicial officer who prepares warrants, writs, etc.; originally, a clerk in the office of the secretary of state.