This is a rare litra from Segesta in Sicily. It is jam-packed with interesting devices: A facing nymph, a dog, a murex shell, a gorgon, and a retrograde inscription. The coin would be quite valuable if the surface hadn't nearly flaked off.
A rough metallic core has been revealed where the surface fell off. In those places where the surface of the coin remains the metal looks good and well preserved: the muscles of the dog are still visible.
Where the surface has flaked off only the barest details remain. The gorgon is barely a face.
I'm not sure how to describe this coin's surface damage. It's chipped. If it was a fourree I would say 'very little silver remaining'. It's not a fourree though, I think it is a genuine ancient silver coin.