Watch List notes:

EUBOIA. Karystos. Circa 350 BC. Chalkous (Bronze, 10.5 mm, 1.31 g, 12 h). Head of bearded Herakles to right, wearing lion's skin headdress. Rev. KAPY Forepart of bull right, horns hung with fillets; behind, club. BCD Euboia 582. HGC 4, 1570. Robinson p. 48, pl. IX, 151. Black patina. Very fine.
From the J. Metzger Collection.

None of the references cited mention the symbol on the reverse (possibly a club) behind the bull forepart, although it is evident in photos of examples that have recently appeared at auction.