This is the Garter Insignia of William Compton (1567/8-1630), first earl of Northampton and Lord President of the Council of Wales, who was elected a Knight of the Garter in 1628.
The Order of the Garter is the oldest order of chivalry in Europe, and was founded on St George's Day, 1348 by the English king Edward III (reigned 1327-77). It comprises the sovereign and twenty-five Knights (now either male or female and elected from any country). The Knights of the Garter are installed in the Chapel of the Order of the Garter at Windsor Castle; each stall in the Chapel bears the stall-plate of each successive Knight. The Northampton set of Garter Insignia is the earliest complete set to survive in England.
The Insignia are gold with translucent and opaque enamelling, set with diamonds and rubies. The Collar of the Order is made up of twenty-five enamelled roses within a garter, alternating with gold knots; there should be twenty-six roses to symbolise all the Knight companions. The 'Great' George is a pendant worn with the Collar, and depicts St George and the Dragon; this is worn when 'full dress' is required. The ‘Lesser' George, a pendant showing St George and the Dragon with an oval Garter, is worn when full dress is not required. The Garter is enamelled with the motto of the Order, HONI SOIT QUI MAL Y PENSE ('Shame on he who thinks evil of it'), and is worn buckled below the left knee.
You are all set!
Your first Culture Weekly will arrive this week.