Diadumenian AE26 of Nikopolis ad Istrum. Magistrate Agrippa. 

K M OPELLI DIADOYMENIANOC, bare head right.
VP AGRIPPA NIKOPOLITWN PROC ICT, city gate, flanked with 
two battlemented towers, third tower rising from centre.

Varbanov 3637 (this coin).

Auction Italo Vecchi 1999, lot 594.