A very similar ewer of the same size and proportions, also bearing a Qianlong four-character mark but with the dragons forming the handle and spout, rather than coiling around them, was included in the Spink & Son exhibition, The Minor Arts of China, London, 1985, no. 213 and later illustrated in R. Keverne ed., Jade, London, 1991, p. 182, fig. 135. This cited example has a white jade cover carved with a similar dragon finial.
Compare with other related examples with covers, the first from the collection of Mr. and Mrs. Edmund C. Bujalski is illustrated in Jade in Chinese Culture, California, 1990, pl. 13; and the other from the collections of Sir Ernest Joseph Cassel and Lady Delamere, inscribed with both Qianlong and Jiaqing six-character yuyong marks, was sold at Christie's Hong Kong, 1 June 2011, lot 3600.
The replacement cover relates well to a spinach-green jade medallion carved in high relief with a coiling dragon among clouds, dating to the end of the 18th century, in the Victoria and Albert Museum, London, illustrated in Antique Jade, London, 1969, p. 119, no. 56.