Mantinea, Arkadia, AR triobol. ca 370-240 BC. 2.61 g. 

MANT, Helmeted head of Athena right.
Head of Kallisto right. 

BMC 16; Traité 966; BCD Pelop. 1480
Very rare. 

With permission of cngcoins.com, March 2011.
Estimate: $150.