This form of drinking cup, with deep body and ring handles with thumb-rests, is known as a skyphos. It was a popular shape, made in metal, pottery and glass during the later Hellenistic and early Roman periods (about 150 BC- AD 100). The cup is covered by a thick glaze of lead silicate glass, which firing conditions turned a deep rich green on the exterior, and honey brown on the interior. The process of producing and firing such vessels was complicated by the adhesive nature of the glaze, which would bond itself to anything it touched in the kiln. The solution lay in firing the vessels upside-down, supported from the inside by three small prongs on a tall stand. The marks left on the interior are small, but drops of congealed glaze which formed when the vessel was inverted appear on the rim. Lead-glazed pottery was one of the few genuinely glazed ceramics of antiquity. At first they were almost certainly made in imitation of metal tableware. The earliest mass-produced and mould-made lead-glazed wares were made in Tarsus, Smyrna and other cities in Asia Minor from the late second century BC. From the late first century BC production centres were established in Italy, in the northern Adriatic and around Rome and Naples. From there the technique was exported to the Empire, from the Danube provinces to Gaul, Germany and Britain.