LATE ANTONINE TO EARLY SEVERAN PERIOD, CIRCA 170-230 A.D.

Circular in form with a raised central cylinder topped with a hemispherical dome, this boss (umbro in Latin) is lavishly embossed and further embellished with cold-worked details. The original appearance would have been bi-chromatic, with the gold-colored relief ornament contrasting with the silver background, achieved via tinning, but now appearing black due to oxidation. At the merge of the cylinder and dome is a protruding ovolo molding. At the center of the dome is a depiction of Minerva seated on a stool, facing to the left. She wears a crested Corinthian helmet high on her head, a long tunic, a scaly aegis, and a scarf-like chlamys that drapes over her left elbow and curves out before her. Her left arm is raised as if to hold a spear, which is not delineated. With her right hand she is perhaps sprinkling incense on to the burning altar before her. The surrounding flange is ornamented with a spread-winged eagle above, acanthus below, and a pelta shields on each side, which are framed by two long snakes that face inwards towards the eagle. Within the open spaces created by the undulations of the snakes are four masks, thought to depict wind gods. The blackened ground is corroded tin, which once appeared as a silvery contrast to the gold-colored designs in shallow relief.

A shield boss was originally attached to the center of a circular shield, with the underside of the dome fitted with a grip. The dome would both protect the soldier’s hand and deflect against enemy strikes during combat. The example presented here is relatively thin, thus it was likely more ceremonial rather than functional. For a copper alloy example of similar form, now in the British Museum, incised with the god Mars surrounded by trophies, eagles and winged victories, see p. 67, fig. 34 in J. Brailsford, Guide to the Antiquities of Roman Britain.