The composition of Mars, Minerva, Venus and Cupid is an attested type produced by the 16th century goldsmith, medallist and gem-engraver Valerio Belli (1468-1546).
The most important part of his career was spent in Rome, where he associated with the artistic and literary set of Michaelangelo, after which he spent time in Venice and finally Vincenza. None of Belli's goldsmith work survives, but some of his best known works are those incorporating rock crystal and precious stones made for his Papal patrons Clement VII and Paul III. Several engraved rock crystals have been separated from the original works they adorned, and bronze plaquettes of his engravings are sometimes found. One particularly interesting group of 50 medals represents ancient mythological figures, some of which were designed to symbolise ancient virtues. Bronze plaquettes were usually made of these works, and of this model six in lead or silver are known (cf. Burns, Collareta and Gasparotto, no.87). However none in rock crystal or lapis are recorded, and rather than being a cast, rock crystal was Belli's supreme primary medium. It is difficult to ascertain whether this would have been an original sixteenth century engraving as part of the Belli series or whether it is a later eigteenth or nineteenth century classical engraving, but it is certainly a fine example of a classicising gem associated with one of the great engravers and goldsmiths of the Renaissance.