Watch List notes:

Greek Coins. Uncertain mint.
Obol, possibly Macedonian mint late V-early IV century BC, AR 0.64 g. Horse grazing l. Rev. Quadripartite incuse square. BCD Thessaly 1437.5 (this coin).
Apparently unique. Struck on a broad flan, light iridescent tone and about extremely fine

Ex Nomos sale 4, 2011, BCD, 1437 (part of).