Gallienus, AE24 of Tium, Bithynia.

AVK P L GALLIHNOC, laureate, draped, cuirassed bust right, seen from the back.
TIA-NWN, river-god Billaeus reclining left, resting left arm 
on overturned urn and, with his right hand, touching with a 
reed a ship's prow before him. BILLAOC in exergue. 

Not in RecGen (177 with different obv. legend and no BILLAOC on rev); SNG v.A.; (cf 1040, ditto); BMC (cf BMC 11 for this rev. legend for Marcus Aurelius); Mionnet; Weber; SNG Cop; 

Ancient Coin Art 2003. Article 3866 (hence the reference).
 Found in an orphaned folder and added June 2010.