According to the inscription, this is Onasos of Pallene, son of Trophimos, a kosmetes of around 129 to 138 CE. Kosmetai were senior administrators of the gymnasium, which was the intellectual and physical training ground, military in origin, for elite youth in Athens. The portrait is mounted on a tall herm (our cast is of only the top half).

A number of portraits of youth supervisors like this survive, usually on herms, from second century Athens. They form a group separate from those of intellectuals and political leaders, the other common subjects for portraits at that time and place