Below is another picture of the coin; however, I am not sure about the reverse legend. Even in hand and in different lighting, holding it at different angles and just staring at it ad nauseum; it is not clear. VICTORIA AETERNA AVGG NN (or some variation) would make sense; but the legend after VICTORIA is not clear. Below is a picture of a Constantine coin from Ostia with a legend of VICTORIA AET AVGGG NNN that is also not in RIC. The emperor on the reverse of each coin is almost identical, but the legend on the Ostia coin reflects the three Emperors (Constantine, Licinius, and Maximinus); while the coin from Arles could only have at most two emperors, as Maximinus II was never recognized on coinage after the Ostia mint transferred to Arles. Perhaps the kneeling figure is meant to represent Maximinus II. Since the style is similar to Ostia coinage, it makes sense that this coin was issued shortly after the Arles mint opened, so Constantine and Licinius would be recognized with a legend that ends with AVGG NN. Since I am not sure of the exact legend, I am putting that part in the description in brackets.
Constantine I
Circa A.D. 313
21mm 3.7gm
IMP C CONSTANTINVS P F AVG; laureate and cuirassed bust right.
VICTORIA [AETERNA AVGG NN]; Emperor on right, in military dress, holding spear, receiving palm branch from Victory; kneeling figure between them [holding offering].
In exergue SARL
RIC VII Arles —