Condor,
I have looked at enlarged views of the action flats as seen on the pictures posted by Cabelas. The original proof marks on the action flats are London. This is further confirmation that the barrels are of Birmingham and not London origin. The quality of the finishing of the action flats[many file marks visible]would not be acceptable to Woodward/Purdey or for that matter any of the Leading Birmingham makers of the era.
In my experience Sidelock shot guns with extractors[ seldom encountered] sell for 30-40% of the price asked for side lock ejector guns of similar quality/condition made by the makers of best guns.
