CaptCurl
You Sir, have a very fine double rifle. How does she shoot and what loads are you using. Do you use .408 or .411 bullets?
Since I am a hunter with double rifles and not a collector, your rifle would be worth much more to me with the 400 Nitro bbls.
How much does she weigh now?
I would recontact Purdey adn have them check their repair records from 1925 to 1955 to see if they can find any info on the rebarreling.