Unknown Minoan, ‘Agate Lentoid’, ca. 1450–1400 B.C., The Metropolitan Museum of Art

Late Minoan II; D. 1/2 in. (1.2 cm)
http://www.metmuseum.org/art/collection/search/248876

Image rights: The Metropolitan Museum of Art (Purchase, by exchange, 1914), licensed under CC0 1.0 Universal