H. Jucker and D. Willers (eds), Gesichter, Griechische und römische Bildnisse aus Schweizer Besitz, Bern, 1982, p. 281, no. 133.
J. Spier, 'A Group of Ptolemaic Garnets', Journal of the Walters Art Gallery, 47, 1989, pp. 21-38, no. 4.
J. Spier, op.cit, lists the above gem and four others similar (two in Bloomington Indiana, one in Munich and one in the Petrie Museum, London) depicting the same ruler, but the Adda example is the only one still in its original ring setting.
The Ptolemaic Dynasty was established in 305 B.C. by Alexander the Great's bodyguard and general Ptolemy 'Soter'. The Ptolemies ruled over Egypt for the best part of three centuries, until the defeat of Cleopatra and Mark Anthony's forces at the battle of Actium in 31 B.C. and Cleopatra's subsequent celebrated suicide. In antiquity the Ptolemies were known by their epithets rather than their number in the sequence of rulers; the identification of their portraits is often open to different interpretation.
In the above intaglio ring, we have a magnificent portrait of a late Ptolemy, his royalty indicated by the broad royal fillet or wreath worn in his hair. The portrait type is known from clay sealings found at Edfu where two types were recognized as depicting King Ptolemy X, Alexander I (107-88 B.C.), and his brother King Ptolemy IX, Soter II. The latter ruled on three occasions, from 116-110 B.C, 109-107 B.C. and 88-81 B.C., being deposed and reinstated as the result of the political machinations of his mother Cleopatra III, and his brother Ptolemy X. He re-unified Egypt and Cyprus and won the support of the Alexandrian population; nevertheless, he incurred their outrage by melting down the sarcophagus of Alexander the Great in order to strike emergency gold coinage. He was eventually murdered.
Fine cameos and intaglio portraits are known from the later Ptolemaic period. Dimitris Plantzos in his monograph Hellenistic Engraved Gems (below) cites a passage in Plutarch (Lives, Luc. 3.1.) "which mentions an emerald portrait of Ptolemy IX set in a gold ring, sent by the king to Lucullus in 85 B.C. This was perhaps the function of the garnets discussed here, and possibly of many more royal intaglio portraits."
For portraits attributed or with possible attribution to Ptolemy IX, Soter II, cf. R.R.R. Smith, Hellenistic Royal Portraits, Oxford, 1988, p. 167, pl. 39, no. 57; J. Spier, 'A Group of Ptolemaic Garnets', Journal of the Walters Art Gallery, 47, 1989, pp. 21-38; D. Plantzos, Hellenistic Engraved Gems, Oxford, 1999, pp. 45-46; and S. Walker and P. Higgs (ed.), Cleopatra of Egypt, British Museum, London, 2001, p. 67, no. 45 and p. 61, nos 28-29.