Pupenius and Balbius were appointed as emperors with equal rights by the senate in April 238. While Pupenius went to wage war against the former emperor Maximius Thrax, Balbenius stayed Rome to attend administration.
Although the two emperors remained in power for only four months, their monetary policy had a major impact on the Roman silver coinage. They issued a great amount of antoninians, in this way replacing the denarius as standard silver coin of Rome. At that time, the silver content of an antoninianus averaged around 40 percent.