The determined look on the face of this enemy of the Roman Empire is in stark contrast to the elegance of the portraits of the emperor and his court. The thick wild hair and light beard indicate that this is probably a member of a Germanic tribe.
It was claimed, with little foundation, that the portrait is of Arminius, the leader of a group of German tribes who won a notable victory over the Romans in 9 CE
Rome, Capitoline Museum 59
Hekler: Greek and Roman Portraits, 280b
Stuart-Jones: Catalogue of the Capitoline Museum (1912), 243, no.59
Found near Naples