Per my wonderfully hefty hardcopy of ERIC II (thanks @Suarez!) this coin seems to be: Val. III - AE4 - 88) B1, O?, R029, T043, M6 ~~ RIC X 2144. However, the Cross has a slight Tau-Rho loop on the vertical bar. The coin is not yet in my possession so I'm posting the listing picture. Thanks in advance for any input!
Definitely Valentinian III, as he is the only "Valentinian" who struck the ae4 type with cross. Also note that the obverse legend is DN VALENTINIANO PF AVG which also is only used on coinage of Val III. BTW, you can just make out CON in exergue on the reverse. As to the possibility of a top loop on the cross, it's certainly just a photo thing and you're seeing the same bar that is at the other three ends of the cross.