Although Commodus was excessive in his depiction of his image, this extreme case is indicative of the objective of many emperors in the exploitation of their portraits.While the emperor is by far the most frequent portrait on the obverse of coins, heirs apparent, predecessors, and other family members, such as empresses, were also featured.
In 192, he issued a series of coins depicting his bust clad in a lion-skin (the usual depiction of Hercules) on the obverse, and an inscription proclaiming that he was the Roman incarnation of Hercules on the reverse.
To aid in succession, the legitimacy of an heir was affirmed by producing coins for that successor.
This was done from the time of Augustus till the end of the empire.
The Romans cast their larger copper coins in clay moulds carrying distinctive markings, not because they knew nothing of striking, but because it was not suitable for such large masses of metal.
Roman adoption of metallic commodity money was a late development in monetary history.
Bullion bars and ingots were used as money in Mesopotamia since the 7th millennium BC; and Greeks in Asia Minor had pioneered the use of coinage (which they employed in addition to other more primitive, monetary mediums of exchange) as early as the 7th century BC.