Cru'Dad's thoughts:
This is a CONSTANTIUS II AD347-348 AE3/4 from the Antiochia mint (now Antakiyah, Turkey). There were 15 Officina parts of the Mint of which the S at the end of SMANS was one. So you could have SMANA, SMANB, SMANZ etc to name a few others. Such a coin is normally 15-16mm dia weighing approx 1.67gm. In the Sears(88) volume it is coin Ref No 4000 Obverse showing D N CONSTAN-TIVS PF AVG with a Diadem Head right. Reverse is VOT XX MVLT XXX in four lines within a Wreath. In RIC Vol VIII it is like Coin Ref No 113 under Antioch Mint page 521 classified as a common occurrence.