Help Needed To Identify Roman Solidusfiivlconstantivs Nobc

Hi guys. I recently bought a book of coins, most of which turned out to be of quite low value, but found this gold coin hiding in there. I've had nothing to do with ancient coins, so was hoping someone out there could help, and this seemed a good forum to start. From what I can gather from the internet, my best bet is that it's from around 330AD.
Obverse- FIIVLCONSTANTIUS NOBC
Reverse- Two soldiers with spear/shield- Can't make it out, but judging by other examples I've seen on the net, I'm thinking it says GLORIA EXERCITVS
Mint- PCONS (3rd workshop- not sure if this gels with 330AD)

I just can't find an exact match out there for the head, although many have been close...




As far as the issue of whether its genuine, there doesn't seem to be any of the obvious signs as denoted on the internet (gives a satisfying tink when dropped onto tiles etc.).

It weighs 2.21 grams, which I understand is unusually light for a solidus, although it does have the two central standards on the reverse (which was subsequently reduced to one as the size of the coin was reduced in later years).

Anyway, that's what I've been able to snoop out. I have no idea of value. It could be anywhere from 300 to 3000 as far as I know. Any approximate value would be also be greatly appreciated.
Thanks for your time.