See a pair of closely related axle caps, similarly cast around the exterior with the slender upright petals, together with their linchpins modeled with boar heads, discovered from a Western Zhou dynasty chariot pit in Jiaoxian, Shandong province, illustrated in CPAM, Changwei District, Shandong Province, 'Report on the Trial Excavation of the Site of Hsian in Chiaohsien, Shantung Province', Wenwu (Cultural Relics), no. 4, Beijing, 1977, p. 71, fig. 15.
Compare also a very similar axle cap and linchpin set, from the collection of J.W. Alsdorf, included in the exhibition Arts of the Chou Dynasty, Stanford University Museum, Stanford, 1958, cat. no. 49; and two others sold in our London rooms, one on 29th February 1972, lot 107, and the other on 15th July 1980, lot 184; as well as an axle cap of the same type, in the Museum of Far Eastern Antiquities, Stockholm, published in Orvar Karlbeck, 'Notes on Some Chinese Wheel Axle-Caps', Bulletin of the Museum of Far Eastern Antiquities, no. 39, Stockholm, 1967, pl. 2, fig. A6, together with a very similar linchpin illustrated on pl. 16, fig. C.