antoninianus

thumb|upright=1.2|Row 1: Elagabalus ([[silver 218–222 AD), Trajan Decius (silver 249–251 AD), Gallienus (billon 253–268 AD Asian mint);Row 2: Gallienus (copper 253–268 AD), Aurelian (silvered 270–275 AD), barbarous radiate (copper), barbarous radiate (copper)]] thumb|upright=1.2 |The antoninianus, introduced in 215 AD, continued the denarius's slow decline in silver purity. The antoninianus or pre-reform radiate was a coin used during the Roman Empire thought to have been valued at 2 denarii. It was initially silver, but was slowly debased to bronze with a minimal silver content. The coin was introduced by Caracalla in early 215 AD. It was silver, similar to the denarius, except that it was slightly larger and featured the emperor wearing a radiate crown, indicating it was a double denomination. Antoniniani depicting women (usually the emperor's wife) featured the bust resting upon a crescent moon.

Even at its introduction, the silver content of the antoninianus was only equal to 1.5 denarii. This created inflation: people rapidly hoarded the denarii (Gresham's law), while both buyers and sellers recognized the new coin had a lower intrinsic value and elevated their prices to compensate. Silver bullion supplies began running short because the Roman Empire was no longer conquering new territory, the Iberian silver mines had been exhausted, and a series of soldier emperors and usurpers needed coin to pay their troops and buy their loyalty. Each new issue of the antoninianus thus had less silver in it than the last, and thus contributed to ever-increasing inflation.