This exceptionally rare piece of early glass is from one of the few types which can be convincingly dated to the Tang period, on the basis of documented archaeological excavation: see An Jiayao, The Early Glass of China, Scientific Research in Early Chinese Glass, Proceedings of the Archaeometry of Glass Sessions of the 1984 International Symposium on Glass, Beijing, 7 September 1984. The earlier excavated Chinese glass, of the Western Han period, largely consist of objects such as bi discs, beads and accessories to mount on swords: in some cases, especially in the case of beads, it is not always easy to distinguish imported material from domestically manufactured objects.

Small glass bottles, of the type which includes this lot, have been found in Tang Dynasty sites since the earliest recorded discovery in 1949. Three examples, with one at least apparently very similar to the present lot, were excavated more recently, at sites respectively in Jinchuan, Gansu Province, and at Xian and Gansu Ningan, Heilongjiang Province. According to the published reports, all are eggshell thin and round, with a long neck and concave bottom. They are recorded as being in effect reliquaries; containers for the ashes of Buddha or Buddhist saints, found in the stupas of Temples. The mouth is carefully fire-polished to form the lip after the vessel was blown; and the neck has a deliberate indentation, which is believed to have some significance to do with the ritual method in which the bottle was filled. While some Tang glass is found blown in shapes which are commonly seen in other Tang material, these reliquary bottles do not have obvious antecedents in Tang ceramics or metal wares. By the time of the Northern Song Dynasty, such "Sarira" bottles from stupas have changed in shape, becoming less spherical and in many cases blown as double gourds: see for example the bottle with large wide neck recovered from a Northern Song Stupa at Lingtai, Gansu Province, op. cit, fig. 19