THRACE, Abdera. Circa 520/15-500 BC. AR Tetartemorion (5mm, 0.11 g). Head of griffin left / Quadripartite incuse square. Cf. May Period I (unlisted denomination). Toned, porous. VF. Extremely rare denomination for Period I at Abdera.
See also Kagan, Small, for a study of the early fractional silver of May's Period I at Abdera, including the first known hemiobols of the period, which were unknown prior to a hoard discovered circa 2000.