Well, the backside looks to be a close as well, so it looks similar to the coin displayed on the page NumiStories. According to this page:
This particular follis was struck in 332 A.D. at the Lugdunum mint, known today as Lyons, France. The portrait shows a young Constantine II facing right in military cuirass and crowned with a laurel wreath denoting his rank as Caesar.
If this is the same, that means this coin depicts Constantine II, and dates to the 3rd century, Roman Empire.