(note: automatic translation; please, allow few days to review it)
The antoninianus (Latin antoninianus) it was a coin used during the empire Romano that had the value of 2 moneys (it is in fact known also as double denarius). Á. the beginning was made out of silver, but you/he/she was gradually devalued up to become a bronze coin.
The coin was introduced with the monetary reform of Caracalla to the beginning of 215 to. C. and it was completely of silver and similar to the denarius unless it was slightly greater and it represented the emperor that a removed crown wore, pointing out so its double value, as in the dupondio that was worth two aces.
The word antoninianus derives from the name of Caracalla (Mark Aurelio Antoninianus); the ancient name of the coin is not known. The coin is defined also removed, from the image of the emperor, even if the term is less precise in how much also used for the dupondis introduced with the monetary reform of Nerone. Different denominations of not-antoniniani produced introduces a removed head, as a coin usually produced following the reform of known Diocleziano as removed post - reform.
In the Antoninianis that represented some figures female (as a rule the wife of the emperor), the bust was introduced poggiante on an increasing (crescent). even if of double value of the denarius, the antoninianus didn't weigh anymore of 1.6 times the weight of the denarius. The denarius continued to be issued close to the antoninianus, but during halves the third century d. C. was quickly devalued for facing the permanent state of war of the period.
After the principality of Gordiano III, the antoninianus replaced completely the denarius that had not beaten in meaningful quantity anymore. As political and economic conditions also worsened the new coin you/he/she was devalued adding copper and pond producing so a league of biglione that seemed similar to the silver. At the half of the kingdom of Gallieno you/they were introduced new methods of workmanship so that the coins continued to appear of silver. The round was produced with a content of very low silver (around 5-10%) and treated with acids in such way that the copper was removed by the surface of the coin leaving therefore a superficial layer of silver. When the rounds so products were beaten a coin it was had with a surface of so thin silver that was brought away leaving the underlying copper open with the use. This coins are usually denominated by the numismatic ones "you silver" in opposition to "of silver."
Nevertheless these measures were not enough to maintain a silver appearance to the coins, pushing Aurelian to reform the antoninianus staring at him/it to a percentage of 20 copper parts for every silver part. This was marked on the reverse of some coins with the Roman figures XXI in west and with the Greek figures KA in the East. These coins have called aureliani. The silvered antoninianus continued to be issued up to the monetary reform of Diocleziano at the end of the 3° century d. C.
During the third century (and perhaps also during the quarter) a lot of imitations of the antoninianus were locally issued wisecracks. It usually refers us to these coins as to removed Barbaric, even if for the more one you/they were produced inside the empire and probably used as you dispatch.