The shape of these large Qianlong flasks is based on Ming dynasty fifteenth century prototypes, which had a convex side that was decorated and a flat unglazed back with a countersunk medallion in the center. For a Yongle (1403-25) example, see the flask in the Freer Gallery of Art, illustrated in Oriental Ceramics, The World's Great Collections, Tokyo, vol. 9, 1981, no. 94. These fifteenth century blue and white porcelain flasks were themselves based on silver-inlaid brass prototypes.
Similar large moon flasks are illustrated in Zhongguo Li Dai Jingdezhen Ci Qi - Qing Juan, Beijing, 1998, p. 169, from the Nanjing Museum; by M. Beurdeley and G. Raindre, Qing Porcelain, London, 1987, pl. 154, formerly in the Edward Chow Collection; in Sekai toji zenshu, vol. 15, Tokyo, 1983, pl. 150, col. pl. 151; and in Porcelain of the National Palace Museum, Blue and White Ware of the Ch'ing Dynasty, Book II, Hong Kong, 1968, pl. 15. See, also, the example sold in these rooms, 22 March 2007, lot 339.