Fangyi appear to be a distinctly Shang bronze vessel shape which was made from the early to the late Anyang period. During this period there were minor differences in the shape and decoration, but no major evolution appeared to take place, as one sees in some other vessel types. The decoration of all fangyi is arranged in three registers, with large taotie masks on the body between small bands of dragons, birds or animals above, and on the foot below, and usually large taotie masks repeated on the cover. For a full discussion of the evolution of the fangyi see R.W. Bagley, Chinese Ritual Bronzes from the Arthur M. Sackler Collections, Arthur M. Sackler Foundation, 1987, pp. 428-44. The earliest fangyi, as represented by those in figs. 77.7-77.9, have a distinctly defined foot with large arched openings and no flanges on the corners, and the covers seen in figs. 77.7 and 77.9 have a straight cant. A slightly later group is represented by figs. 77.10-77.15, which appear to be of two types: those with flanges at the corners and those without, like the present vessel. On all of them the body continues into the foot in a straight tapering profile and the covers have a slightly convex profile. It is into this group that the present vessel fits.
See, also, C. Deydier, Archaic Chinese Bronzes, vol. I, Xia & Shang, France, 1995, p. 213-8, where the author illustrates fifteen fangyi from different public and private collections, showing the differences and similarities found on these unusual vessels. Two of these are very similar to the present fangyi, one from a private collection, p. 215 (1) and the example from the Avery Brundage Collection, Asian Art Museum of San Francisco, p. 218 (bottom right).