Rough guess is that you are looking at a John Rigby that was put together in California when US investors owned the name.
Does the rifle have "London" engraved anywhere on the barrel? A (true) Rigby made rifle would usually have this and that is where most of the value comes from.
A phone call or email to London with the serial number and details will get you the provenance of the rifle.
California made Rigby rifles do not typically carry the resale of London made rifles, from what I have seen.
