constantin gold coin id

Please help me id this coin from constantin i have search on the internet but i cant find it , i want to now wich constantine and the year
its a gold coin

Front side : Consthantinus IV nnod
lady sitting whit a child : rommia
best regards// hernan

The legend makes me think of a Constantinus II:
http://www.wildwinds.com/coins/ric/constantine_II/t.html
CONSTANTINVS IVN NOB C
date :
http://en.wikipedia.org/wiki/Constantius_II
corrections welcome