n the Roman Empire, the coins were used as politic propaganda tool, with the images of the emperors on the obverse and sentences to celebrate the exploits and his worth.
The transformation already seen from the anonymous coinage to the celebration of the moneyers' ancestors, knew a further step with Julius Caesar, using coins with his portrait. This approach was also adopted during the imperial period, with the image of the head of the Roman government used for strengthening the personification in the emperor of the state and its laws.
An additional step was the association of the image of the emperor with those of the divinity, to affirm the supernatural origin of the emperor's power. This tendency was already shown during the fight against Pompey, in which Caesar minted coins with images of Venus and Aeneas, to support the hypothesis of his divine nature. This tendency was pushed to the maximum by Commodus, who proclaimed its divine state minting in 192 a coin that represented its bust dressed with a skin of lion on the obverse, while on the reverse a legend proclaimed him as the reincarnation of Hercules.
Another usage of the coin was to legitimate the succession to the throne. Since August up to the end of the empire, the representation of ancestors was replaced by the ones of the family and of the heirs of the emperor, strengthening the public image of the candidate to succeed the throne.
The result of the use of the coin as mean of communication and the independent mintage of coins from the Roman provinces produced an extreme variety of types.
Concerning the different typologies, the most common coin in the Roman world up to the III sec. A.D. was the Sestertius (silver at the beginning, and then in bronze), whose value was low enough to avoid fractions, but also strong enough to be used in the common exchanges.