In the summer of 1767 untrained enamelers began to work at the Court at Beijing producing wares which would evolve into the Guyue Xuan wares of the last decades of the reign. The name Hu Xuan, arrived at by combining the first two characters of the Guyue Xuan to get the common family name Hu, appears only on very early examples of this group of experimental wares. Before long, as the enamelers honed their technical and artistic skills and as they did, the Guyue Xuan mark became standard. See H. Moss, "Mysteries of the Ancient Moon," JICSBS, Spring 2006, pp. 16-33, where the author illustrates a number of examples with the same hallmark (figs. 4-9), and discusses the Guyue Xuan enameled wares, also mentioned in the note to lot 304.