RIC does not list this issue with a dot in the mintmark. I don't really believe that the dot is actually part of the mintmark though, but rather part of the horse-- the right hoof. It's a sharp example and just sold for US $124.70.
Constantius II
A.D. 350- 355
22mm 5.8gm
D N CONSTANTIVS P F AVG, pearl diademed, draped & cuirassed bust right.
FEL TEMP RE-PARATIO Soldier spearing fallen horseman who is reaching up with one arm, Γ in left field.
In ex. •ANAI
RIC VIII Antioch 132