Watch List notes:

ELIS. Olympia. 95th Olympiad, 400 BC. Tetartemorion = 1/4 obol (Silver, 8 mm, 0.22 g, 3 h). [FΑ] (retrograde) Eagle's head and neck to right. Rev. Τ within a circular incuse. BCD Olympia 87 (this coin). Seltman pl. VIII, 18 (but the obverse letters are off the flan on this coin). Extremely rare. Boldly struck, lightly toned and attractive. Minor scratches on the obverse, otherwise, extremely fine.
From the "Collection sans Pareille" of Ancient Greek Fractions and from the BCD Collection, Leu Numismatics 90, 10 May 2004, 87.

The Τ on the reverse stands for the denomination - see the following lot.