For a long time the supreme power at Rome was vested in the consuls who held office for one year. Naturally anyone elected to this high position was anxious to inform everyone holding any high place or office of his accession to the dignity, and the usual way of doing this was to send round diptychs of ivory announcing the event, as well as subsequent ones concerning any other important matters which might occur during the consulate.
Fig. 15.—Ivory diptych, of the consul Valentinian, A.D. 380.
Not only was the communication inscribed upon the wax, all of which is now gone, but the outside ivory was carved with invaluable portraits, scenes and inscriptions. By examining these carvings we can frequently ascertain who was the consul that issued them, and often enough we can find his portrait carefully drawn. In one of the many excavations made in the Forum at Rome, tablets containing a list of Roman consuls were found, and these serve as an official check upon our interpretation of the records existing upon the consular diptychs.
Consular diptychs were generally larger than the wooden pugillaria, which were always small. Ivory diptychs are rarely less than six or seven inches in length.
The privilege of giving away finely carved ivory diptychs was highly esteemed, and in the fourth century the Emperor Theodosius issued an edict forbidding any but one of the two consuls, one at Rome and the other at Constantinople, to issue them.
In the matter of consular and official costume the Roman carved ivory diptychs are of great importance.
Figures often appear on coins or gems, but they are always very small. On the diptychs, however, they are sufficiently large to show full details. The subjects depicted on them are various. There are games, combats in the circus, scenes from the Passion, boys emptying sacks of prizes, figures of Saints, Adam and Eve, busts and portraits of consuls both in medallions and full length. The best collections of consular diptychs are to be found at Rome, Milan, Monza, Paris, Munich, Berlin, Liverpool and London.
Besides the consular there are also ecclesiastical diptychs, the majority of which were probably only diverted from their original intention and altered and adapted to a new use. The original wax was removed and new inscriptions engraved on the ivory, mostly lists of martyrs or benefactors to the particular church which had possession of the diptych.