Plaquettes are small, metal (usually bronze) relief sculptures, an art form developed in Italy in the 1440s. They are usually larger than medals, often round, rectangular or oval in shape, and have a religious or classical scene on one side only. They almost never have portraits or inscriptions. While some plaquettes were used as objects of decoration, or attached to furniture or utensils, they were also used as portable sculpture, seminal in the transmission of artistic ideas and information, first in Italy and then throughout Europe.
The design is inspired by a classical sarcophagus then in the Medici collection, depicting the fall of Phaeton (or Phaethon). The classical myth is retold by Ovid in the Metamorphoses, describing how Phaeton, the son of the nymph Clymene and the god Apollo, wishes to see his father and be acknowledged as his son. He travels to the Palace of the Sun and meets Phoebus Apollo, who grants him any wish he desires. Phaeton asks to drive his father's chariot of the sun across the sky for one day, and despite Apollo's reluctance, does so - only to plunge the earth into disaster. Zeus saves the world by throwing a lightning bolt at Phaeton, striking him down. He falls, hair aflame, and is received by the river Eridanus. Pope-Hennessy argues that the subject is actually the death of Hippolytus, and the Phaeton reference is actually to the sarcophagus.
In Euripides' play Hippolytus, the son of Theseus, offends the goddess Aphrodite. She makes his stepmother Phaedra fall in love with him. Hippolytus is horrified and the rejected Phaedra kills herself, blaming him in a deathbed letter. Theseus believes her and exiles Hippolytus, who is dashed to pieces in his chariot when the sea-god Poseidon, prompted by Aphrodite, sends sea-monsters to madden the horses. Pope-Hennessy says that because 'the sea is represented at the base of the plaquette', it is Hippolytus depicted here rather than Phaeton, who falls into a river.
Whatever the subject, the plaquette is a tour-de-force of composition and execution. Moderno is claimed as 'the most accomplished designer of plaquettes in Italy in the Renaissance,' and here he solves the problem of the circular format by accentuating internal circular rhythms. The horses' crimped manes and tails swirl around the large curves of their bodies, contrasting with the gentle curve formed by the dead youth.