Sicily, Aitna. Circa 400-350 BC. AE Hemilitron (24mm, 18.29 g). 

AITNAIW-N, head of Athena right, wearing Corinthian helmet.
Horse prancing right; M above. 

Calciati III pp. 141-143, 1; SNG ANS 1301 (part 5); Virzi 527. 

With permission of cngcoins.com, auction 64, Lot: 42.