For a discussion of the Official School of hard-stone carving, see Moss, Graham, Tsang, A Treasury of Chinese Snuff Bottles, Vol. 2, Quartz, no. 258 and the several subsequent examples which are all of the school.
This is one of the masterpieces of probably Qianlong-period bottles of this School, with extraordinary use of the natural colors of a remarkable piece of stone, since the very unusual, thin upper layer of grey coloring is repeated on three sides of the bottle, allowing the carver unusual latitude in using it to advantage in his carving. For other masterly bottles with horses from this school, see Moss, Graham, Tsang, The Art of the Chinese Snuff Bottle. The J & J Collection, Vol. 1, nos. 134, 151 and 153, where the symbolism of the fat and thin horses combined in a single subject is given, explaining that one represents the honest official (the thin one) who remains poor and honest, the other the corrupt official, who gets fat through his corruption. Such bottles were probably distributed as a reminder by the Court to officials, but might also have been given between officials, also as a reminder to serve the Emperor loyally and the people honestly.