When coins are minted in ancient fashion, metal on the surface gets liquid for a second, and characteristic patterns form that can be seen on many Roman coins, of "streams" from inside to outside (
see some examples here). Presence of them is a good sign, but in no way a requirement (coin minting was not exact, temperature may have varied, and so in some cases there was more flow, in others -- none, not to mention that patterns may have gotten worn off in time). Also, with some modern faking methods they can create an imitation of these flow lines. If you are interest in all this, you can go to
Fake Ancient Coin Reports , there are a lot of discussions and photos of different fakes, including specific faking methods. You can also go to the
FORVM there (this link is the specific part where they discuss fakes) and even show your photos and ask them to analyze it.
But at the end, as I said, nobody can tell you for sure, there may be only suspicions one way or the other.