The current owners of the Thomas Turner name have confirmed that the records of the original firm have been lost, so this statement can only be supposition, in spite of Jack Rowes' assertion (how old is he?). As ALF has pointed out, Turner's business did fold in 1912, but we don't know precisely when he ceased to be Jeffery's primary finisher of rifles. As you rightly state, Jeffery's sales up to WWI was prodigious, and much of this business was never recovered after the war, particularly for double rifles since most of the skilled workers had been killed in that conflict, and by then the Mauser magazine rifle was in the ascendancy. But to give you (and other members)a "snapshot" of Turner's involvement in Jeffery's rifle business, here is an except from his Order Ledger in the pre-WW1 period;

It shows that Turner had a hand in all of the rifles listed, from Falling Block's in .22WCF, .256, .400S, .303, Martini's in .256, .303, a 303 Enfield, a .404 Mauser, and a .400S Double!

Jeffery may well have turned to other suppliers and finishers after Turner's demise, but there is no doubt that the success of Jeffery's rifle business was largely founded on the quality of the product that he sourced from Turner. To contend otherwise is ludicrous.

As for the numerical breakdown of finisher's of Jeffery's double rifles vis-a-vis Turner and Jeffery, since Turner's records are lost, and Leonard's also presumably gone, who really knows, apart from those that have accessed Jeffery's records? Even then, his Shop Ledgers are missing, and only his Order Ledgers survive. These do not give a complete picture of his operation, since they don't give complete details, only who he paid the bills to - so if the finisher made or bought in parts, such as barrels and actions, it is not itemised.

As for A.Hollis, here is a copy of page 122 of Wal Winfer's 3rd Volume in his "The British Single Shot Rifle" series of books;

If anyone has anything other than addresses on barrels or business addresses in England to support the contention that he was anything other than a gun retailer, in the mould of Jeffery (albeit primarily located in India), perhaps they could add to the sum total of knowledge on him??