Gergis, Troas, AR Hemidrachm, 11 mm, 1.84 g. 350-300 BC. 

Sphinx sitting right.
Head of gorgoneion facing within incuse circle

Boston MFA 2324 (unattributed); SNG Fitz 4614 (unattributed). 

With permission of Numismatik Naumann, auction 53, Lot 139, May 2017.