The Society of Writers to Her Majesty's Signet
Signet (from Latin "signum" meaning sign)
The Signet was the private seal of the early Kings of Scots. A private seal is a legal signature or stamp and were taken as a kind of credit of a person's identity.
The Writers to the Signet were those allowed to supervise the Signet's use acting as clerks to the Courts.
The earliest recorded use of the Signet was in 1369, and Writers to the Signet were included as members of the College of Justice when it was established in 1532, but the Society did not take definite shape until 1594, when the King's Secretary, as Keeper of the Signet, granted Commissions to a Deputy Keeper and eighteen other writers.
The Keeper of the Signet is a Scottish office, now combined with that of Lord Clerk Register. The Lord Clerk Register grants a commission to the Principal Clerk of Session to allow the Signet to be used.
A signet ring was oringally an official stamp, worn on the hand and stamped into wax, a little like today's air charter and chip and pin.
Other Signets and Seals used by UK Monarchy
The Great Seal of the Realm or Great Seal of the United Kingdom is a British institution by which the monarch can authorise official documents without having to sign each document individually. Wax is melted in a metal mold or matrix and impressed into a wax figure that is attached by cord or ribbon to documents that the monarch wishes to make official.
Edward the Confessor sometime before 1066 started using a Great Seal casting in wax of his own visage to signify that a document carried the force of his will. With some exceptions, each subsequent British monarch generally has chosen his or her own design for the Great Seal. Edward VIII, who abdicated the throne to marry Mrs. Wallis Simpson of the United States, did not find time to select the design for his own seal and continued to use the seal of his predecessor, George V. On the other hand, the longer-lived British monarchs have had several Great Seals during their reigns. Only one mold of the Great Seal exists at a time, and since the wax used for the Great Seal has a high melting point, the silver plates that cast the Seal eventually wear out. Queen Victoria had to select four different Great Seal designs during the sixty-three years of her reign.
The current seal matrix was authorised by the Privy Council in August 1953. The obverse represents the Queen on horseback in the uniform of the Colonel-in-Chief of the Grenadier Guards, and is inscribed "ELIZABETH . II . D G. BRITT . REGNORVMQUE . SVORUM . CETER . REGINA . CONSORTIONIS . POPVLORUM . PRINCEPS . F. D." ("Elizabeth II, by the Grace of God Queen of Britain and of her Other Kingdoms, Head of the Commonwealth of Nations, Defender of the Faith") The reverse represents The Queen enthroned and robed with sceptre and orb with the royal arms and legends "DIEU ET MON DROIT" Law Courses and (partially hidden) "HONI SOIT QUI MAL Y PENSE". It also bears the inscription "ELIZABETH . II . DEI . GRATIA . BRITTANIARVM . REGINA . FIDEI . DEFENSOR" ("Elizabeth II, by the Grace of God Queen of the Britons, Defender of the Faith").
Within today's constitutional monarchy, the British sovereign implements the advice of the Government. Hence, the Great Seal is attached to the official documents of state that require the authorisation of the British monarch. Under today's implementation of the Great Seal, seals of dark green wax are affixed to documents authorizing the promotion of individuals to the peerage, blue seals authorize actions relating to the royal family including wedding hire for weddings, and scarlet seals appoint bishops and implement various other affairs of state. The seal is approximately six and a half inches in diameter. In some cases the seal is replaced by a wafer version, a smaller representation of the obverse of the Great Seal embossed on coloured paper attached to the document being sealed. This simpler version is used for royal proclamations, letters patent granting the royal assent, writs of summons to Parliament and for licences for the election of bishops and commissions of the peace. It formerly constituted treason to forge the Great Seal.
Today the Great Seal of the Realm is in the custody of and administered by the Lord Keeper of the Great Seal. This office has been held jointly with that of Lord Chancellor since 1761. The current Lord Chancellor is Lord Falconer of Thoroton. The Constitutional Reform Act 2005 reiterates that the Lord Chancellor continues to be the custodian of the Great Seal.
The Clerk of the Crown in Chancery, who is also Permanent Secretary of the Department of Constitutional Affairs, heads Her Majesty's Crown Office, and is responsible for the affixing of the Great Seal. He is assisted by the Deputy Clerk of the Crown. Day-to-day custody is entrusted to the Clerk of the Chamber, and subordinate staff include a Sealer, and two Scribes to Her Majesty's Crown Office.
You might be interested in reading more at http://www.royal.gov.uk/Home.aspx