As most of you know I'm not good with ancients. That is new territory to me so please correct me if I'm mistaken on this coin.
There are over 150 types of Fel Temp-Reparatio of Constantius II, reaching barbarian, no special marks, from several cities. Pictures are poor. If nobody can read the mintmark, nobody will correct you, nor will agree.
The mintmark just is not complete enough; it likely begins with SM but then the important info is just unclear (H is possible,though). As CATADC explained: there are 1549 different coins in the name of Constantius of this particular type. Limiting is possible on the basis of size and other variables, but even if the first letters are SMH it could be RIC 61, 65 or 90. as I see no letters or symbols in the fields. Frans
This is the closest I had in Heraclea (sold it a while back) but with the unclear photos there is nothing much to be said. The shirt on the barbarian is striped on both and general style suggests it is likely Heraclea.