Here's a sharp example with what is probably old collection numbers in the right field of the reverse.
Without even seeing the legend, you can differentiate coins of Quintillus from those of his brother Claudius by the hair. Quintillus has curly hair, while Claudius has straight hair.
Quintillus
A.D. 270
Ӕ Antoninianus
17x20mm 2.7gm
IMP QVINTILLVS AVG, radiate, draped and cuirassed bust right, seen from behind.
FIDES MILIT, Fides standing facing, head left, holding standard in either hand.
In ex. S
RIC V Mediolanum 52
Superb portrait, don't think I've seen better!