Your coin is actually Constantine the Great minted at Thessalonica and struck in 324AD.Attribution
Constantine I - Thessalonica Mint - AE3 - RIC VII 123
Obverse: CONSTAN_TINVS AVG, Laureated head right
Reverse: D N CONSTANTINI MAX AVG, Laurel wreath enclosing VOT/XX with TSepsilonVI in exergue
Here is another example below that shows a clearer mint mark.