This striking pair of fittings appears to be related to a group of openwork masks in the shape of a demon's or animal's face hammered out of a thin sheet of bronze which adorned the heads of horses pulling chariots. An openwork bronze mask of a demon of similar size (26.5 cm. high) dated to the Western Zhou period, from the Lucy Maud Buckingham Collection, The Art Institute of Chicago, is illustrated by S. Fontein and Tung Wu, Unearthing China's Past, Museum of Fine Arts, Boston, 1973, p. 48, no. 13. The authors discuss, pp. 49-50, the excavation of a chariot burial in Fengxi county, near Xian, Shaanxi province, between 1955-1957 which revealed similar thin bronze openwork masks which were fitted between the ears of the horses. The fact that the present pair of plaques is shown in profile rather than front-faced would suggest they were perhaps intended for attachment to either side of the head or to the harness.
Similar depictions of dragon heads seen in profile with mouth agape to expose large fangs can be seen on smaller bronze fittings dated to the Western Zhou illustrated by H. Brinker, Bronzen aus dem alten China, Museum Rietberg, Zurich, 1975, pp. 157-8, nos. 130-1.