It is, or at least it is supposed to be, a Roman Republican silver denarius. Specifically,
this coin from 113-112 BC. The obverse portrait is of Roma, who is almost always depicted with a winged helmet. The unusual feature of this coin is the ornate ring, or "torc", surrounding the portrait; this is apparently a reference to an ancestor of the coin-issuer having defeated a Celtic chief in hand-to-hand single combat, winning his torc (and thus obtaining his new Latin family name, Torquatus).
It's an interesting story, but the type is not one of the rarer ones in the Republican series. There are no fakes of this type listed on FORVM, either. SO I would assume it was genuine unless you have other reasons to believe otherwise.
Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis