You can deduce some information from the length of the
legend. On this coin you can see clearly it begins CONSTA (no D N or FL
IVL at the beginning of the
legend) and seems to have only room for maybe 2 more letters on the left of the
bust, and maybe 5-6 on the right. From that I'd conclude that
Constans is more likely, as
his name is so much shorter, and that
CONSTANS -
P F AVG was the most likely of the
obverse legends used. If you are sure about the
mint being
Thessalonica I'd be more certain - it would have to have 5 letters in the
exergue for this
type (SMTSA, SMTSB, Γ, Δ or Ε).
Steve