In the appreciation of jewelled gems, it is worth noticing the two-layer agate cameo with the profile of Louis XV bearing the signature of the famous Marquise of Pompadour, the most powerful French woman in the eighteenth century and official mistress of the beloved sovereign of France. In addition to its acknowledged political influence, the marquise of Pompadour has a very important role in the functions of patron of the Arts, a task that exercised thanks to the solid friendships that bounded her to famous artists. Among these, is worth mentioning the most famous stone engravers of the era, who was in the court of the King: Jacques Guay. It is indeed under the direction of Guay that the Marquise refined with particular success the art of carvings cameos: they often depicted the effigy of her royal lover, which she did not hesitate to wear in public, fiercely flaunted on the wrist with spectacular bracelets or rings on the fingers. Another example of a cameo ring with the portrait of Louis XV, with the same characteristics and equally signed by the Marquise, is today preserved in the collection at the Cabinet des Medailles at the National Library of France in Paris.