History has not been kind to Diadumenian. Born around 208 CE to the emperor Macrinus and his wife Nonia Celsa, the boy, whose full name, Marcus Opellius Antoninus Diadumenianus, was almost comically longer than his reign, was elevated to co-emperor in 218 CE at the age of just nine or ten. His father, a former Praetorian prefect of Moorish origin, had seized the throne after orchestrating the assassination of Caracalla, making theirs a dynasty built on deeply unstable foundations. His reign lasted mere months before Elagabalus, backed by the Severan legions in Syria, defeated Macrinus in battle. Even though Diadumenian was still a child, both father and son were captured and executed.

Struck in Rome between May 217 and mid-May 218 CE, this type which portrays Diadumenian as Caesar has a very interesting combination of reverse imagery and legend. The legend states PRINC IVVENTVTIS, translated as "Prince of Youth", yet depicts Diadumenian in military garb, holding a standard in his right hand and a short scepter in his left, with two grounded standards to his right. While juxtaposing Caesar's youth and supposed military skill, it was a perfectly conventional image for a Caesar-in-waiting. This negates the fact that the boy was barely 10 years old!