"Gonzaga Cameo"

Is a three-layer sardonyx cameo, one of the best examples of ancient glyptics.
It is a couple portrait. Most likely, this is an image of the Hellenistic pharaohs of Egypt - spouses who were both brother and sister - Ptolemy II Philadelphus and Arsinoe II. Made in the III century BC by an unknown author in Alexandria of Egypt.

Interesting fact:

The onyx from which the cameo is made has a hardness of 6-7 on the Mohs scale, about the same as window glass and the best modern tool steels. Ancient artisans worked such materials with tools of inferior hardness, using corundum powder with a hardness of 9. Experts estimate that it would take more than a decade to make a cameo using this technique.