Vologases IV, King of Parthia. Edessa mint, ca 147-191 AD.
AE Tetrachalkon, 20mm, 7.25 g. 

Diademed bust left, wearing tiara with flap and decorated 
with horn and “hooks”; B behind.
Large symbol resembling O on reversed T. 

Sellwood 84.134; Shore 436; BMC Parthia 96-99 (under Vologases III).
VF, green and brown patina. Rare. 

With permission of CNG, cngcoins.com, Auction 88, Sept 2011, lot 586. Sold for 260 USD