The Antoninianus 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, and was a silver coin similar to the denarius except that it was slightly larger and featured the emperor wearing a radiate crown, indicating that it was a double denomination. Antoniniani depicting females (usually the emperor's wife), featured the bust resting upon a crescent moon.