This superbly cast and enamelled censer is almost identical to the one in the collection of the Palace Museum, Beijing, illustrated in Enamels - 3 - Cloisonne in the Qing Dynasty (1644-1911), Compendium of Collections in the Palace Museum, Beijing, 2011, pl. 226.
The shape of this censer is based upon ancient bronze vessels. The blade-shaped legs, loop handles and flanges, along with the wide spreading taotie masks, all have their prototypes in Zhou dynasty bronzes, many of which are illustrated in Xiqing gujian, 'Inspection of Antiques from the Zhou Dynasty', the catalogues of ancient bronzes in the Qing Court Collection compiled under the authorization of the Qianlong emperor in 1755. Compare also to a Qianlong-marked fangding with cover, also decorated with taotie design and with flat dragon-form legs, is in the collection of the National Palace Museum, illustrated in Enamel Ware in the Ming and Ch'ing Dynasties, Taipei, 1999, no. 59. Further examples from the Qing Court Collection include two censers in the Palace Museum, one dated to the early Qing period and with a gilt openwork cover and lion finial, the other with a Qianlong six-character mark but without a cover, illustrated in Enamels - 2 - Cloisonne in the Qing Dynasty (1644-1911), Compendium of Collections in the Palace Museum, Beijing, 2011, pls. 68 and 245.
Compare also to a Qianlong-marked example from the Mandel Collection, sold at Christie's Hong Kong, 30 May 2012, lot 3908.