This is a common but was a fun one when I identified it, because of the reverse legend.

IVL CRISPVS NOB C / CAESARVM NOSTRORVM, struck Siscia.
I knew legends about 'our lord' from medieval coins. This was the first roman I noticed as a possible model.
Vows for 5 years. He made it that long. His father would only kill him in his tenth year as caesar. Constantine, like most emperors, was not a nice man.
Not a very nice portrait, some day I will do better for this common emperor. But it serves as my Crispus.