From the Romanov era, period of Tsar Alexander II (the Tsar Liberator) each gold link enameled in black with white cogwheels, attached by oval link chains. Enamel slightly chipped as seen in images.
Mid 19th century, hallmarked 56 Link-1/2 in. (1.3 cm) diam.; length of chain-3/4 in. (1.9 cm)