I can't see what the symbols are shown on the reverse, but the front is certainly a Roman person (everyone else carried beards, or had long hair if female). It seems like early Byzantine. Since the person doesn't have a beard, it's definitely older than the reign of Emperor Heraaclios (610-641), who was the first Roman Emperor who didn't shave (besides Julian the Apostate (361-363), but he's an exception; every Emperor after Heraclios had a beard). If the symbols on the reverse are Christian, since Christianity wasn't legal before 313 AD and thus couldn't be printed on coin, then it's probably from the period between that year and 610.
If you cleaned the front up, you could read the text and see who the person is, and thus we could date and locate the coin's origin. But if you intend to sell the coin to a collector, don't clean it up with rough tools. They could damage the coin and greatly reduce its value.
PS: The oxidation looks green. If that is oxidation. Is it made of copper?
PS2: Put a piece of paper over it. Then scribble over it with a graphite pen. You should be able to see the imprints of the text. Please tell me what it says.
PS3: My friend's parents both deal with numismatics, so I've sent her the pictures. Maybe we'll get a professional answer.
PS4: What size is it, in millimeters? Thickness, diameter? Is it flat, or concave?
I'll take a guess based on the look of the face: either Valentinian I, or Theodosius I. That's the 2nd half of the 4th century AD. And I think the coin is a follis, a small copper or bronze coin minted since the reign of Diocletian (284-305).