Watch List notes:

WESTERN ASIA MINOR, Uncertain. Late 6th-early 5th centuries BC. AR Tetartemorion (6.5mm, 0.19 g). Head of horse right / Rough incuse square. CNG E-345, lot 321; otherwise unpublished in the standard references. VF, lightly toned. Good metal.

The horse head / incuse type is a fairly common fraction, but none of the published examples (cf., e.g., Klein 332) closely matches the style of this piece.