Constantine I, SAC MONN AVGG ET CAESS NN, a forgery?

[Nikko]

I got this scarce coin on eBay a few minutes ago, but I'm not 100% it'd it's authenticity. The overall appearance is not bad, but it's a little weird.
Any opinions are welcome.
Thanks

[Victor]

I can see why you might have some doubts, but it is hard to be sure from just a photo. It has some characteristics of a cast, but the reverse has a particularly genuine looking bit of greenish corrosion at the end of the legend, on the first N of N N. Hopefully in hand it will be obvious if it genuine or not.

[Nikko]

I finally got it and I'm 99,9% confident it is a genuine anche nice coin.