Watch List notes:

IONIA. Kolophon. Circa 450-410 BC. Tetartemorion (Silver, 7.5 mm, 0.35 g, 9 h). Laureate head of Apollo to right; behind his head, laurel branch. Rev. Monogram of ΤΕ within a shallow incuse square. Milne, Colophon 32. With a head of Apollo of fine style, well-struck and nicely toned. Nearly extremely fine.
From the "Collection sans Pareille" of Ancient Greek Fractions, ex Münzen und Medaillen FPL 451, January 1983, 27.

The monogram on the reverse stands for the denomination.