The denomination was initially a very small silver coin struck sporadically during the Roman Republic. It was revived early in the imperial period and was issued from the 1st century AD to the middle of the third century AD. The sestertius is highly valued by numismatists since the large size gave celators (engravers) a large area to work with. High quality examples can sell for over a thousand dollars, while extremely worn specimens can be obtained for under $20.
During the end of its issue, when sestertii were reduced in size and quality, the double sestertius was issued first by Trajan Decius and later in large quantity by Postumus. It was distinguished by the radiate crown worn by the emperor, which wa also used to distinguish the dupondius from the as and the antoninianus from the denarius.
See also: Roman currency.