Silver antoninianus, 21mm, 3.81gm, issued AD 251. Rome mint.
Obv: Q HER ETR MES DECIVS NOB C, Radiate, draped bust facing right.
Rev: PRINCIPI IVVENTVTIS, Apollo seated left holding laurel branch and resting arm on lyre.
References: Sear 9522, RIC 146, RSC 24a.