There were three emperors who were named "Antoninus Pius" on their coins. Rather than calling them "Antoninus Pius I, II and III", the emperors are known to history as Antoninus Pius, Caracalla and Elagabalus. The obverse legend "IMP ANTONINVS PIVS AVG" is only known on the coins of Elagabalus. The reverse type is the emperor himself standing offering a sacrifice over a small altar.
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Unlike many ancient Roman coins, this one can be dated to within a year: the reverse inscription reads "PM TRP IIII COS III PP". The fourth year of tribunician power of Elagabalus was in 221 AD.
Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis