Celadon vessels of this type are discussed by Julian Thompson in the article 'Chinese Celadons', Arts of Asia, November - December 1993, pp. 60-72, where the author states that the present jar and cover "must be one of the finest recorded", citing the supurb modeling of the dragon and dog, the perfect bluish-green color of the glaze - of the preferred hue refered to as Kunita by the Japanese - and its remarkable condition, having escaped the effects of degradation associated with burial.
It appears that jars of this type originally appeared in pairs, one bearing around its shoulder the 'green dragon of the East', the other the 'white tiger of the West'. A pair of these jars in the Percival David Foundation is illustrated by M. Medley, Illustrated Catalogue of Celadon Wares, London, 1977, pl. IV, no. 36. Medley suggests they may have been filled with aromatic oils and then placed on their respective sides of the deceased, whose head would have been to the north.
A nearly identical jar and cover from the Avery Brundage collection in the Asian Art Museum, San Francisco, is illustrated by M. Tregear, Song Ceramics, New York, 1982, col. pl. 286, and another from the Shanghai Museum is illustrated in Zhongguo meishu quanji; Gongyi meishu bian; Taoci (The Great Treasury of Chinese Fine Arts; Arts and Crafts; Ceramics), Shanghai, 1988, vol. 2, no. 204.