Sicily, Syracuse AR Tetradrachm, c. 420, signed by 'A'. 

Biga walking right; above, Nike flying left crowning charioteer.
Diademed bust of Arethusa right, hair bound in sakkos 
ornamented with maeander pattern and inscribed with 
the letter A; around, four dolphins swimming to right. 

Boehringer 709 (but with the A on the sakkos not noted). Very rare.
 
Note: A truly exceptional depiction of Arethusa by an
 unknown master engraver who was the first at Syracuse 
to sign his dies.

Contributed by Roma Numismatics Ltd. April 2010.