Mantinea, Arkadia, AR obol. ca 340-320 BC. 12mm, 0.63 g. 

Helmeted head of Athena right.
Large M within dotted circle. 

BMC 17; Traite II-3, 968; BCD Pelop. 1483; HGC 902. 

With permission of cngcoins.com, June 2012.
Estimate: $150.