Valentinian SECVRITAS REIPVBLICAE, a bit deformed and the mintmark is falling off the edge. Am I seeing SMHA or SMKA or am I completely off base? I lean that it is an H for Heraclea, but the obverse looks more similar to examples from Cyzicus (K). Namaste!
There is also a Nicomedia mintmark of SMNA. Cyzicus is the most common though. You should also post the obverse, since it helps (sometimes)