This coin has a small dot between the banners at the top; not to be confused with the centering dot. It's a small dot (bigger than the centering dot), perhaps something left over from the engraving process or perhaps some form of workshop control.
Constantine I
A.D. 332-333
18mm 2.6g
CONSTANTI-NVS MAX AVG; rosette-diademed, draped and cuirassed bust right.
GLOR-IA EXERC-ITVS; Two soldiers helmeted, stg. facing one another, reversed spear in outer hands, inner hands on shields resting on the ground; between them two standards with • between them at top.
in ex. TR•S
RIC VII Trier 537 var.