The custom of allocating a birthstone to each month of the year or zodiac is now nearly ubiquitous in western cultures, the popular and most widely accepted list of birthstones having been codified by the American National Association of Jewellers in 1912. The concept’s origins however, are ancient, and have their roots in both Christian and Jewish texts, appearing in Exodus as the stone inlays of a holy breastplate worn by the High Priest Aaron, and later in New Testament as the twelve foundation stones of the New Jersualem that appeared before St John in the book of Revelation. The number twelve had significance in these contexts – most immediately as parallels to the twelve tribes of Israel, and the twelve disciples of Jesus Christ. The stones were each thought to embody a particular virtue associated with their relevant apostle or tribe. In daily life they also aligned with the twelve months of the year, and additionally with the twelve signs of the zodiac. Tiffany’s chief gemmologist George Frederick Kunz, an important figure in the scientific classification and connoisseurship of gemstones, was also fascinated by the alleged supernatural properties of these materials and their meanings in religious and mythological contexts. In his book ‘The Curious Lore of Precious Stones’ (1913), Kunz traces the appearance of birthstone jewels back to 18th century Poland, perhaps even earlier, and attributes the spread of the custom to its popularity with the widespread and cosmopolitan Jewish communities throughout Europe. As demonstrated by this complete set, with each plaque fitting interchangeably into the central ring, at this time it was customary to wear each stone for the duration of its corresponding month in order to harness the stone’s benefits at their most powerful. This intact set of early birthstone jewels is extraordinarily rare. Stylistically, the cut-cornered outline of each plaque, combined with the glass ground and the closed settings of the stones points to a late 18th century century date. As so few comparable pieces have survived, this set offers a fascinating and quite possibly unique testimony to the evolution of this modern custom.