Solidus (Coin) Portraying Heraclius and His Son Heraclius Constantine

From the Art Institute of Chicago record

After Christianity became the official religion of the Roman Empire, the Byzantine emperors adopted Christian themes and symbols, most notably the cross, to stand for both the religion and the political state on their coinage. The previously ubiquitous profile portrait head was replaced by frontal or full-body depictions. Christ dominated the iconography, and Greek titles and phrases came to replace the Latin ones. On the front (obverse) of this coin, the Byzantine emperor Heraclius is shown alongside his son, Heraclius Constantine; there is a cross between them. On the back (reverse) a Greek cross stands on a set of steps.