It was the custom for Consuls to present to senators and other
officials these little folding ivory tablets, and the adornment
of Diptychs was one of the chief functions of the ivory worker.
Some of them were quite ambitious in size; in the British Museum
is a Diptych measuring over sixteen inches by five: the tusk from
which this was made must have been almost unique in size. It is
a Byzantine work, and has the figure of an angel carved upon it.

Gregory the Great sent a gift of ivory to Theodolinda, Queen of
the Lombards, in 600. This is decorated with three figures, and
is a most interesting diptych.

The earliest diptych, however, is of the year 406, known as the
Diptych of Probus, on which may be seen a bas-relief portrait of
Emperor Honorius. On the Diptych of Philoxenus is a Greek verse
signifying, "I, Philoxenus, being Consul, offer this present to
the wise Senate." An interesting diptych, sixteen inches by six,
is inscribed, "Flavius Strategius Apius, illustrious man, count
of the most fervent servants, and consul in ordinary." This
consul was invested in 539; the work was made in Rome, but it
is the property of the Cathedral of Orviedo in Spain, where it
is regarded as a priceless treasure.

Claudian, in the fourth century, alludes to diptychs, speaking of
"huge tusks cut with steel into tablets and gleaming with gold,
engraved with the illustrious name of the Consul, circulated among
great and small, and the great wonder of the Indies, the elephant,
wanders about in tuskless shame!" In Magaster, a city which according
to Marco Polo, was governed by "four old men," they sold "vast
quantities of elephants' teeth."