Although often only slightly larger than the as, the dupondius was worth twice as much since it was made of a more highly prized golden colored bronze alloy, while the as was made of reddish copper. The dupondius is distinguished from the as by the radiate crown warn by the emperor. Some dupondii from the time of Nero and before lack the radiate crown, making them hard to distinguish today due to heavy patination of specimens, which obscures their original color.
See also: Roman currency.