Weighs 5.5g
Diameter 28mm - 30mm
A clear M is visible representing 40 nummis
CON For Constantinople mint
Officina - Є = 5
I think i can see a 
on the right representing 6th year of reign but not entirely sure
some form of star like symbol see similar 3rd picture above the M
Reverse seems to be 2 or 3 figures wearing crosses 4th picture is the closest i could find
2 coins were similar in design but my coin is larger in diameter
40 Nummi - Constans II
40 Nummi - Heraclius
Any help is appreciated