Not enough examples of this type come from an archaeological context to establish a finite chronology; a handful of fragments from the western provinces of the Roman empire belong to the first century C.E. Other similar examples are Eisen, pl. 40, Hayes, no. 47, Fitzwilliam Museum, no. 32c, Constable-Maxwell Collection, lot 38, and Grose, no. 234. - Ancient Glass in the University of Colorado Museums
The shape of the rust damage indicates either a repair of a large break, or that at one time the bowl was on display on a bad metal mounting, presumably propped up like a modern decorative plate. Museum, Henry P. Colburn - Ancient Glass in the University of Colorado