This is an electrotype replica of a gold seal showing a lion found in Mycenae Shaft Grave III in 1876 by Heinrich Schliemann. The replicas were created by Emile Gilliéron in the late 19th century and manufactured by the Württemberg Electroplate Company. Many museums acquire such replicas for display purposes.
Bibliography
Evans, Arthur. 1935. The Palace of Minos at Knossos, IV, p. 546, fig. 507
Myres, John (ed.). 1936. British Archaeological Discoveries in Greece and Crete 1886-1936, p. 29