Watch List notes:

ATTICA, Aegina, (500-480 B.C.), silver stater, (11.87 g), obv. smoothed shell sea turtle with row of dots down dorsal spine, with countermark of a horse to left in centre of shell, rev. "windmill" [four sunken segments, wedge shaped, (S.1854, Asyut Group IVb "heavy collar" cf.500-506 particularly 502, cf.SNG Delepierre 1509). Bright, fine - very fine, countermark fine, making it very rare.

Ex Ponterio and Associates, Sale 102, 29th July, 1999 (lot 167 part).
Asyut hoard suggests the chronology to be 500/490-480 B.C.