I think probably unofficial. As you say the
style is wrong for
Rome, in addition to the unexpected laureate vs diademed
bust. There's another one the same in the
ANS collection whose picture I've attached.
The other possibility is that it's meant to be
Constantine II rather than I and the
reverse legend is wrong (or it's a
mule), but again I think the
style speaks against that. While the caesars are also only listed with left facing busts, the second coin below sold on
eBay in 2007... I'm not sure whether it's official either though.
Your coin gives an appearance of being underweight/sized in addition to the other issues, which would also point to it being unofficial.
Ben
