With its integrally carved trefoil handle, deep dodecahedral bowl, and massive gilt mounts, this cup is as rare as it is spectacular. There are few surviving examples of Western medieval lapidary. Indeed, medieval European vessels carved from semiprecious stone are so little known that preserved examples are sometimes mistakenly attributed to the imperial courts of Rome and Byzantium. The confusion is one that would have delighted the cup's creators.

Carved from a material that is immediately perceived as precious and exotic, the vessel is a product of the imperial court of Charles IV (crowned at Rome 1355; d. 1378). Its jasper, with characteristic amethyst inclusions, could have been mined only in the foothills of the Ore Mountains, northwest of Prague. A sixteenth-century source tells of the emperor's sending men there to search for semiprecious stones to decorate his cathedral and royal chapel. In recent years geologists have found traces of their work in abandoned shafts dating to the Middle Ages tucked into the mountains near Ciboušov. Today Bohemian jasper still sheathes the chapel walls at Prague Cathedral and at Karlstejn Castle, just outside the city. Often vessels of this period have lost their original mounts or have been embellished by subsequent owners. The Museum's cup, remarkably, retains its medieval mount, which bears comparison to goldsmiths' work created in Prague and preserved in the cathedral treasury.