Watch List notes:

GREEK COINS
LESBOS

Unattributed early mint. Circa 500-450 BC. Stater (Billon, 18mm, 11.29 g). Two calf's heads confronted, forming a single facing head; between them, laurel tree. Rev. Incuse square. SNG Copenhagen 285. SNG von Aulock 1682. Traité I, pl. XV, 14. Toned and very clearly struck. With a fascinating optical illusion on the obverse. Unusually well-preserved. About extremely fine.

Ex Bank Leu 2, 25 April 1972, 237.
Lesbos seems to have specialized in unusual types that could be viewed in two ways: the two calves' heads on the obverse either can be seen as separate animals facing each other, or as a single head facing the viewer (albeit with two necks!).