It has been suggested that this distinctive group of enamels was produced for the Court at some distant facility, Yangzhou being the most likely place, some time shortly after the construction of the Guyuexuan for the Qianlong Emperor in 1767. They are usually marked either with a pale Qianlong reign mark or a Guyuexuan mark in iron-red, such as the present example. For another example of a Yangzhou enamelled glass bottle in the collection of The Victoria and Albert Museum, from the Gulland Bequest of 1907, see H. White, Snuff Bottles from China, London, 1992, pl. 60, no. 2.