Source of Arlelatum -> Constantia name change date ?

[Heliodromus]

Victor, do you happen to know the source of the 328 AD date for the name change of the city of Arelatum to "Constantia" ?

If wondering if there's a solid (or at least non-numismatic) basis for the date, or if this just follows the dates assigned to the coins ?

[Victor]

No, I don't recall any ancient sources that mention it. Bruun in "The Constantinian Coinage of Arelate" doesn't mention any ancient sources either, just his reasoning for the dating to 329; which by RIC VII he revised (in agreement with LRBC) to 328.

[Heliodromus]

Thanks, Victor.

I suppose that speaks for itself - if Bruun was reasoning about the date he can't have been aware of any definitive source.

From the Arles campgates we can see the name change while the pearl diadem was in use (ARLP S-F -> PCONST S-F), before the rosette-DC (E8) bust in the following PCONST T-F mark, which obviously agrees with generally accepted dates for these bust types.

The name change must have happened at essentially the same time as the Trier mint apparently stopped the campgate series short, since the final Trier campgate, RIC 510, actually has a rosette diadem (E2), not the rosette-DC (E8) given in RIC. If Trier had been producing bronze in 329 we might have expected a rosette-DC to follow.