Caligula and Rhoemetalkes III. AE28, Kingdom of Thrace. AD 38-46. 14.49 g. 

GAIW KAISARI SEBASTW, laureate head left.
BASILEWS ROIMHTALKAS, diademed and draped bust of Rhoemetalkes III right. 

RPC 1724; Jurukova 210.

With permission of Helios Numismatik auction 6, lot 129, March 2011.