As Sovbloc notes, it's a Remington 1858 pattern. It looks odd in several ways: the loading lever shape is far from standard pattern, the grip looks odd, and the cylinder seems somehow strange. No visible markings. We need proof marks and makers mark to tell more. Sometimes under the loading lever on the barrel. It's a brasser, so if working would only be suitable for light loads.
Is it allegedly functional? Without more information like markings, I would lean towards non-Italian replica and not necessarily functional or safe to fire.