Hi Buckstix

First, congratulations on getting such a fine rifle. I particularly like the early doubles

It could have been made by many of the trade gunmakers in London as the proofs are London, otherwise Birmingham would be the clear favourite

I also have seen many doubles in the hand and in books but like you, I have not seen such cone shaped firing pins

Clearly early with Percussion type hammers (flash slots at top)

My first thoughts were W&C Scott or Phillip Webley who made most double rifles for Holland & Holland before 1892 and with Evans "With H&H for 12 years" he would be very aware of their quality but the London proofs?

But then I saw this pic

Courtesy Donald Dallas

A similar cone firing pin and securing screw but on a later rifle, (side as against back action locks) maybe for special order?

Hopefully someone will come up with more info

Good luck

Tony