The technique seen here is termed "snake" thread decoration because of the serpentine manner in which the trail wanders over the surface to create abstract designs. It was practiced in both the eastern and western areas of the Roman Empire, though current scholarly opinion suggests it originated in the East and quickly spread to the West (D.B. Harden, "Snake Thread Glass Found in the East," in JRS 24, pp. 50-54). For a similar example in the Ernesto Wolf Collection see no. 62, p. 166 in E. M. Stern, Roman, Byzantine, and Early Medieval Glass, 10 BCE-700 CE.