Signet rings, engraved with a coat of arms, owner's initial or the mark used by a merchant to identify his goods are amongst the most common types of surviving medieval and Renaissance rings. The engraved bezel of the ring was pressed into sealing wax and this was then fixed onto a letter or deed. They were made of gold, silver or bronze, depending on the means of the owner and continued to be widely used until the 18th century when they were largely replaced by fob-seals, worn on the watch chain. The coat of arms was the heraldic motif, generally enclosed in a shield shape, which was used as a sign of identity by some wealthy families or individuals. The use of heraldic arms was regulated by tradition and later in England, by the College of Arms.

A particularly glamorous type of signet was developed in the 16th century. The coat of arms or heraldic device was engraved onto a hard stone such as rock crystal, or in this case, a pale sapphire. The colours of the coat of arms could be painted onto foil which was placed under the stone. This allowed the carved stone to be pressed into hot wax without fading the bright colours on the ring. This ring was made for a member of the Savoia of Carpi family, who had close ties with the Papal court. His arms are shown incorporating the insignia of the Gonfalonier of the Holy Roman Church, a ceremonial office which entitled him to bear the papal banner.

This ring forms part of a collection of 760 rings and engraved gems from the collection of Edmund Waterton (1830-87). Waterton was one of the foremost ring collectors of the nineteenth century and was the author of several articles on rings, a book on English devotion to the Virgin Mary and an unfinished catalogue of his collection (the manuscript is now the National Art Library). Waterton was noted for his extravagance and financial troubles caused him to place his collection in pawn with the London jeweller Robert Phillips. When he was unable to repay the loan, Phillips offered to sell the collection to the Museum and it was acquired in 1871. A small group of rings which Waterton had held back were acquired in 1899.

Edmund Waterton used the fortune which was made by his family’s involvement in the British Guiana sugar plantations to put his collection together. His grandfather owned a plantation known as Walton Hall and his father, Charles Waterton, went to Guiana as a young man to help run La Jalousie and Fellowship, plantations which belonged to his uncles. When slavery was abolished in the British territories, Charles Waterton claimed £16283 6s 7d in government compensation and was recorded as having 300 enslaved people on the Walton Hall estate.