Item one: for an ancient coin type and family portraits of Trajan and Plotina, cf. G. M. A. Richter, Gems of the Romans, London, 1971, p. 112, nos 542-543. For an 18th Century cornelian example, cf. M. Henig, M. Whiting and D. Scarisbrick, Classical Gems, Ancient and Modern Intaglios and Cameos in the Fitzwilliam Museum, Cambridge, 1994, p. 294, no. 615.