Here's young Commodus -- Commodus as a BABY!! Faustina II, AD 147-175. Roman orichalcum sestertius, 24.65 g, 30.4 mm, 12 h. Rome, AD 161. Obv: FAVSTINA AVGVSTA, bare-headed and draped bust, right. Rev: SAECVLI FELICIT SC, draped throne on which there are two infant boys (Titus Aurelius Fulvus Antoninus and Commodus), with stars above their heads. Refs: RIC 1665; BMCRE 936; Cohen 193; RCV 5282; MIR 27. Here's a close-up:
Bought my Commodus denarius few months ago. I liked that it can be easily attributed, the price was decent and it is somewhat scarce. RIC III Commodus 169 Date Range: AD 187 - AD 188 Obverse Legend: M COMM ANT P FEL AVG BRIT Type: Head of Commodus, laureate, right Reverse Legend: P M TR P XIII IMP VIII COS V P P Type: Salus, draped, seated left on low seat, feeding from patera in right hand snake coiled round altar
It's an interesting question - for which my answer is: yes, the portrait can help you to date the coin. Here's a post (linked to a relevant publication by from Andreas Pangerl) that might interest you: Dating Caracalla.