I wish some close members could confirm that the reverse of this LRB includes a clear cross within the upper square of the standard. The Emperor on the obverse seems to be at a very early age. I feel it's a sweet sandy patina coin. Am I right...
Although I'm unsure which Emperor it may be (perhaps Valentinian or whomever). I'm fairly certain the standard would contain a Chi-Ro at the top...since that was a common design theme at that time---as many coins of the era would attest.
Since the type was used by six emperors and we don't have a single letter of the name, the hope for ID is in the face. Is the mintmark CONST? Is the face Gratian or Valentinian II? I'm not sure I could ever be sure but perhaps someone with experience of a thousand of these coins would find it obvious.