Maximinus II.
Obverse: IMP C GAL VAL MAXIMINVS P F AVG
Reverse: IOVI CONSERVATORI AVGG
Mintmark: A in field, SMHT in exergue, Heraclea mint
Cataloge number: RIC VI 74
I can't find it in the Numista cataloge, but you can find an example here: https://www.wildwinds.com/coins/ric/maximinus_II/t.html, if you search for RIC VI 74, A