below is an excerpt from RIC about this type-
“A gateway may denote an imperial Adventus, but it is worth noting that earthquakes in 429 and 443 gave rise to considerable concern about the walls and other public buildings in the city. During the later fourth century, the legend, which specifically refers to the festival of 3 January, was often associated with consular issues.†(RIC X pg 173)
Valentinian III
A.D. 425- 435
13mm 1.3gm
DN VALENTINIANVS PF AVG; Pearl diademed, draped and cuirassed bust right.
VOT PVB (public vows); Campgate with two turrets and Q between them.
In ex. RM
RIC X Rome 2124