Wild;

After reading your reply, I viewed again the photo of the barrel flats and what I thought at a quick look was strikeovers with a tool by the proof house are indeed original London proof marks. My apologies.

I also wondered who "C.O." was. Dallas (book) does not list a Purdey employee with those initials in his 1875 list, however the list he viewed at Purdey's is not likely complete; and they could also be the initials of one of Purdey's barrels testers. Dallas also says that Purdey's barrel list is available for the time frame of the gun under discussion; and I would suggest that you ask Purdey to view the barrel book as well.

BV