Sounds nice so far...

Get some photos up, detail the areas where the wood and metal meet, the proof marks under the barrel flats and on the action flats, and any other marks that are on the gun.
What kind of sights are on the gun, is it set up for scope mounts -- are they present, does it have set triggers -- do they still work or need tuning, are the bores ok, have the chambers been damaged, is there a cartridge trap in the stock, what kind of action is it, is it cased -- is it the original case and does it include the original accessories, has it been refinished or restocked...
Lots of things determine the value of a double rifle.

From there, it's condition condition condition...
The group here can give you a pretty fair suggestion on how much the rifle is worth, if you want a complete diagnosis of how the rifle's doing *what kind of shape it's really in* you can send it to a gunbuilder like JJ Prudeau at Champlin arms for an evaluation. That will cost you money.

--Tinker