Compare the similar gold-inlaid bronze mechanism illustrated by Cheng Dong and Zhong Shao-yi in Ancient Chinese Weapons - A Collection of Pictures, Beijing, 1990, p. 144, no. 6-58 a-c. The mechanism is shown in profile (a) beside drawings of the back of the mechanism and sight (b) which indicates similar linear markings or measurments on the back of the sight similar to those of the present mechanism, and the top (c) indicating similar gold inlay. Athough not specifically dated, it is most likely late Western Han, as a later mechanism of similar type, similarly inlaid in gold and dated to the Three Kingdoms period (220-265) is illustrated p. 169, no. 7-26, and in line drawings nos. 7-27 and 7-28. See, also, the similar gold-inlaid bronze mechanism dated late Han/Western Jin dynasty, 1st-4th century AD, illustrated by C. Delacour, De bronze, d'or et d'argent: Arts somptuaires de la Chine, Musée Guimet, Paris, 2001, pp. 139-41, where the different parts of the mechanism and the method of using a crossbow are explained.