Vermeule: Banded glass paste intaglio gem. Green, blue and white agate. (Modern gilt ring setting) Omphale walking left, with attributes of Herakles. Graeco-Roman.
Berges, Dietrich K. Antike Siegel und Glasgemmen der Sammlung Maxwell Sommerville: im University of Pennsylvania Museum of Archaeology and Anthropology. Mainz am Rhein: Verlag Philipp von Zabern, 2002. Page/Fig./Plate: 78 See: p. 62, no. 316, taf. IV; taf. 58
White, Donald J., Ann B. Brownlee, Irene B. Romano, and Jean M. Turfa. Guide to the Etruscan and Roman Worlds at the University of Pennsylvania Museum of Archaeology and Anthropology. Philadelphia: University of Pennsylvania Museum of Archaeology and Anthropology, 2002. See: p. 79, no. 118
Vermeule, Cornelius C. The Sommerville Gem Collection of the University Museum of Archaeology and Anthropology. The University Museum, 1956. See: no. 178
