Stuart crystals are faceted rock quartz crystal jewels which originated as a form of mourning (or protest) jewelry after the execution of King Charles I of the House of Stuart in 1649. The first Stuart crystals were pendants or rings and featured the initials of the king or a portrait of him done in miniature under a rock crystal top. Later variations included cufflinks, buttons, earrings, and slides, in addition to the original pendants and rings. Some of these 18th century versions, like this lovely ring, featured a simple hair work background. This piece is extra special because the underside of the head is engraved with two sets of initials: "IP" and "CP".