Here is the response from Purdey:

Dear Mr Dunn,
I have not see in our records any link
between Purdey's & Army & Navy csl not even stock guns being sold to them.
I am not aware of licences for other gunmakers being sold to make the self
opening action. I believe the first gunmaker to use this action other than
Purdey's was Henry Atkin in 1907 long after the patent had run out.
I hope this information is useful.
Yours sincerely

David Maynard