The double sestertius was an ancient Roman coin devised as a way to add value to regular sestertius coins, and were first introduced by Trajan Decius. So-called double sestertii were not actually made with twice the amount of orichalcum, or brass, and they ignobly fell out of favor.
The colorful ruler Postumus used double sestertius coins in his breakaway republic, and his overstrikes are popular with coin collectors.