Theantoninianus orpre-reform radiate[1] was acoin used during theRoman Empire thought to have been valued at 2 denarii. It was initially silver, but was slowlydebased tobronze with a minimal silver content. The coin was introduced byCaracalla in early 215 AD. It was silver, similar to thedenarius, except that it was slightly larger and featured theemperor wearing aradiate crown, indicating it was a double denomination.Antoniniani depicting women (usually theemperor's wife) featured the bust resting upon a crescent moon.[2]
Even at its introduction, the silver content of theantoninianus was only equal to 1.5 denarii. This createdinflation: people rapidly hoarded thedenarii (Gresham's law), while both buyers and sellers recognized the new coin had a lower intrinsic value and elevated their prices to compensate. Silverbullion supplies began running short because theRoman Empire was no longer conquering new territory, theIberian silver mines had been exhausted, and a series ofsoldier emperors andusurpers needed coin to pay their troops and buy their loyalty. Each new issue of theantoninianus thushad less silver in it than the last, and thus contributed to ever-increasing inflation.
In 271 AD,Aurelian increased the average weight of theantoninianus, this change lasting for only a short time. Around this time, the enigmaticXXI was first marked on the reverse of theantoninianus. The true meaning of this series of numbers is still a topic of debate, but is thought to represent a 20:1 silver ratio (4.76% silver, which may originally have been 5%, if worn-away silver enrichment on the surface is allowed for).
By the late 3rd century AD,antoniniani were almost entirely made ofbronze reclaimed from melted-down older issues like thesestertius. Vast quantities were minted, with a large percentage of the circulating stock beingcontemporary forgeries, often with blundered legends and designs. Individual coins were by then practically worthless, and were lost or discarded by the millions. The resultant situation was not unlike thehyperinflation of theWeimar Republic in 1920sGermany, whenpaper money was printed in reckless abundance. The coin ceased to be used by the end of the 3rd century, when a series of monetary reforms attempted to arrest the declineby issuing new coinage.
Today most of these coins are extremely common finds, with a few scarcer examples includingAemilianus,Marcus Aurelius Marius,Quietus, andRegalianus.
Modernnumismatists use "antoninianus" because it is not known what it was called in antiquity. An ancient Roman document called theHistoria Augusta (of generally low reliability) refers to silver coins named after an Antoninus on several occasions (several Roman emperors in the late 2nd and early 3rd centuries bore this name). Because Caracalla's silver coin was a new issue, and he had taken Antoninus as part of his imperial name, an association (though likely false) was made with it, and the name stuck.
