This is a brass dupondius, also called an as, minted in Nemausus, also called Nimes, in the Gaul (near France) region of the ancient Roman Empire. Typical weights run between 11 and 13 grams, with diameters near 27 mm. The two portraits are Augustus, also called Octavian, first Emperor of Rome, and his boyhood friend Agrippa. On the reverse, a crocodile is chained to a palm tree.
The coin in our picture (upper left) sold for 130 euros (about $138 US dollars) during a 2015 auction by Jean Elsen et ses Fils in Brussels. Thanks to Jean Elsen for granting copyright release to CoinQuest.
Although counterfeits are possible (see secondary picture to right), genuine coins catalog approximately as follows:
worn: $30 US dollars approximate catalog value
average circulated: $200
well preserved: $600