Imperial diptych offerings to the emperor. However, the fact that the Barberini ivory was almost certainly not a diptych, but some kind of imperial icon without a second panel is a serious argument against the existence of the imperial diptych type. The two panels representing the empress Ariadne, in the Bargello in Florence and the Kunsthistorisches Museum in Vienna, also belong to the hypothesied imperial diptych type. They are the only central panels of such a diptych (other than the Barberini ivory) to survive, since all other fragments of such diptychs are from side panels. Imperial diptych In Late Antiquity, an imperial
Beaune Altarpiece different. The figures occupy distinctly separate niches and the colour schemes of the grisaille saints and donors contrast sharply. Like many mid-15th century polyptychs, the exterior panels borrow heavily from the "Ghent Altarpiece", which was completed in 1432. The combination of naturalistic donor portraits with grisaille imitation statues of saints is borrowed from that work, as is the treatment of the Annunciation. Van der Weyden used iconography in the Beaune exterior panels not found in his other works, which suggests Rolin may have commissioned the altarpiece to follow van Eyck's example. Van der Weyden was not inclined merely to imitate