Here is a note I got from an online gun dealer:
Dear Mark:
Yes, despite the condition, a London made gun with Purdey's name and address on the rib, will have some value (hundreds perhaps, not thousands).
Since copyright and trademark laws were not enforced, we often see guns made in Liege, Belgium, proof marked (E over LG), or those made in Birmingham, England, that have spurious Purdey (or Manton, or other famous names) marked on the locks or barrels.
Send images to for our good faith estimate.
Appraisal of damaged guns requires close inspection,
From what little I can see, that sounds to be a pretty fair assessment. I know a lot of people have mentioned in this thread that it is a worthy restoration project, which it very well may be. Be prepared though, having a proper restoration done on this gun will most likely cost more than the gun is worth, regardless if it a Purdey or not.
