Here is a nice example of a VLPP with a dot on the helmet. I have seen other examples and you can also find them with a star, but both are rare.
Constantine I
A.D. 319-20
20mm 3.1gm
CONSTA-NTINVS AVG; laur. helmet, cuir. bust right.
VICT dot LAETAE PRINC PERP; two Victories stg., facing one another, together holding shield inscribed VOT PR on altar inscribed with the letter I.
In ex. ASIS*
RIC VII Siscia 93