Superbly engraved on this convex ringstone is Diomedes stealing the cult statue of Athena, known as the Palladion, from Troy. The robustly muscular hero, nude but for a cloak at his back, leaps over a rectangular altar, holding the statue of Athena in one hand and a sword in the other. A star and a crescent moon in the field indicate that the raid took place under the cover of darkness. Before him stands a nude male cult statue with one arm raised, and a reclining figure, perhaps the slain temple guard, protrudes from the side of the altar. Behind Diomedes is a palm branch leaning against a short column.
Trojan stories were very popular on Roman gems, including the stealing of the Palladion, which would guarantee sucess for the Greeks. Both Odysseus and Diomedes were involved in the theft of the statue, and they can appear alone on gems, as here, or together, as on the Felix Gem in Oxford (no. 10.20 in M. Henig and A. MacGregor, Catalogue of the Engraved Gems and Finger-Rings in the Ashmolean Museum: II, Roman). The Sangiorgi Diomedes is similar to a nicolo ringstone in the Beverly Collection (op. cit., no. 157), but in reverse. Boardman and Wagner suggest a mid-1st century B.C. date, while Moret considers it Flavian.