Minted by Constantine (and his sons) to commemorate the two cities of Rome and Constantinople.
Constantine moved the capital to Constantinople - this rightfuly cheesed off the Romans. The VRBS ROMA is a way of placating the citizens whilst also commemorating the city's 1100 years on the top of the pile. Unfortunately, its been downhill since then for poor Rome.
The other coin, CONSTANTINOPOLIS, commemorates the founding of Constantinople in Byzantia - the city needed residents, I'm sure this got the word around effectively because these things are bleedin' EVERYWHERE.
Heres IDs for the two with mint marks left, the other two have problems on one of the sides - one is just corroded on one side, the other has a mortar like encrustation which isn't leaving any time soon.
VRBS ROMA D4 left none 2 TRS dot Trier RIC VII Trier 529 c3 330-331 AD
CONSTANTI-NOPOLIS N1 left none R wreath epsilon Rome RIC VII Rome 387
And FR - I've tried my hand at a nicer background. Oddly, the best I could find was also a pillow case!

