Silver antoninianus, 22mm, 4.23gm, issued AD 250/251 Rome mint.
Obv: Q HER ETR MES DECIVS NOB C, Radiate, draped bust right.
Rev: PRINCIPI IVVENTVTIS, Herennius, in military attire, standing left, holding wand and transverse spear.
References: Sear 9523, RIC 147c, RSC 26.