A splendid example of highly prized workmanship from the 4th century AD, the Trivulzio Diatreta Cup (known by the name of the collector who brought it to Milan in the 18th century) is a luxury cup consisting of an inner beaker and an outer cage of decoration with circular geometrical patterns and an inscription. The cup was part of the rich funeral kit laid in the marble sarcophagus of a high-ranking personage buried in the Novara Area (Italy).
The vessel, in colourless glass, is decorated with a web made of four rows of brown and blue tangential circles linked with a cross motif at the points of contact. Around the cup surface runs an inscription in Latin “BIBE VIVAS MULTIS ANNIS” meaning “Drink! May you live for many years”.
The inscription, similar to others that appear on this genre of glass, suggests it was used as a recipient for wine. Given its rarity and value, it is likely that it was used exclusively at the imperial court or maybe for cult ceremonies. It has also been suggested that the shape of the outurned rim of the beaker, and the missing stand of all known vessels, might mean that all diatreta were like the example in the Corning Museum of Glass, which was almost certainly an oil lamp designed to be suspended. It is therefore possible that bowl-shaped cage cups were hanging lamps rather than drinking vessels.
Cage cups belong to a class of rare precious manufactured objects produced in specialised workshops, active perhaps in the Rhineland-Danubian area (Germany), in Northern Italy, in Illyria (Albania and Dalmatian coast) and in the East, or by an itinerant craftsman at the service of the Imperial Court.
The Trivulzio Diatreta Cup is the only specimen of cage cup with no damage at all. Two other good examples of cage cups are the Munich Cup and the Cologne cup, both found in Cologne. Cage cups are the most exclusive luxury glasses made in the later Roman Empire.
References: Wikipedia, Glass of the Romans
Bibliography: Glass of the Caesars (1987), Donald B. Harden, Hansgerd Hellenkemper, Kenneth Painter, and David Whitehouse