One of the first 'true' Imperial dupondii, issued specifically on orichalcum and with radiate crown to denote the difference in value. This standard, set during Nero's reign, would remain constant for the duration of the dupondius. It would also set the standard for the radiate crown denoting the 'double' value, the same principle was applied to the antoninianus to differentiate it from the denarius. - Thanks to Steve McBride for the description