Beautiful coin. Yes, such beauty is rarer among LRBCs - both in their original state and they way they often exist today - but it is not unheard of. There are many interesting designs and lovely examples.
The one in your image appears to be
silvered. Could just be a trick of the camera but it does appear to have the remains of
silvering in many places. The
silvering was quite thin by this time - I suspect they used a very different
silvering process from what was being used in, say 318 - 324.
As for the banner the Emperor is clearly holding it with the front facing away from us. I say that tongue in cheek as it makes no sense to engrave it like that but that is clearly what it looks like with the hand visible on the pole in front of the banner and no design visible on the banner. Maybe passive resistance of a die-hard Pagan engraver....
Shawn