The reliquary, linked by documentary sources to the skull of St. Prassede, has the appearance of a silver-gilt quadrangular case decorated on the fronts and sides with embossed reliefs, and with a lid coated with cloisonné enamels. It was reduced to its present form during the pontificate of Nicholas III (1277-1280), whose seal it retains. On the main faces, there are two pairs of Saints depicted in full figure, projecting from the background surface. At the top of the cover there are twelve plates, circular in shape, probably corresponding to the series of the Twelve Apostles (only three survive today), originally arranged around a rectangular slab, with Christ enthroned between the Virgin and St. John, according to the Byzantine scheme of the “Dèesis”. While the fluidity of the reliefs and their elongated form are reminiscent of the characters of late tenth- and early eleventh-century ivories, the extraordinary range of colours used in the images displays striking similarities with Georgian jewellery items dating from the same period, allowing the geographical origin of the glazes to be connected with this particular stylistic area.