Watch List notes:

LESBOS, Mytilene. Circa 412-378 BC. EL Hekte – Sixth Stater (10mm, 2.51 g, 4h). Helmeted head of Ares right / "Helmeted" head of Amazon right in linear border within incuse square. Bodenstedt Em. 65 (rev. die ζ); HGC 6, 991. VF.

The Amazon on this reverse die clearly does not appear to have a helmet, but Bodenstedt argues that this was due to a mistake by the engraver.