Good question, Tim, but with the British system of using outworkers difficult to answer.

The founder of the Guildford business, Richard Jeffery started in about 1850. A very nice single percussion rifle by him featured in DGJ not long ago. To what extent it was built in his workshops and to what extent he bought in the lock (probably) the Damascus tube (probably) and had it rifled (quite likely) by specialists we are never likely to know.

There is an August 2020 article in Diggory’s Vintage Gun Journal about a Richard Jeffery gun made for him by E.C. Hodges in Islington.

In the 1960’s they appear to have been primarily retailers of guns built by others, but if Lord Onslow had walked into their shop and said “build me a best gun regardless of expense” they could no doubt gone to an actioner, barrelmakers, a stocker and finisher and a best S.R. Jeffrey gun would have emerged from their front door.

They seem to have had family links with various other Jeffery gunsmiths, and is possible that at one time they shared workshop facilities.