There were quite a few British Gunmakers that made guns almost exclusively for the trade. Firms like Webley & Scott are well known as trade suppliers, but is is not often appreciated that there were a host of other gunmakers, such as as Osborne, Leonard, Saunders, Tranter, Turner, Ellis, Robertson (of Boss fame), etc., that made for the trade. These makers did sell some guns signed by themselves, but mostly they sold guns to other retailers in various states of finish from barreled actions to fully finished (engraved and signed). Some of these retailers might simply have been Ironmongers in small provincial towns wher they serviced a local market. My guess is that few double rifles were sold this way, which is why you see most double rifles carrying the names of more recognised firms. As well, a few retailers, Jeffery included indulged in such nefarious practices as re-using parts from guns made by other makers.

When you glance through "Gunmakers" sales ledgers, you have to realise that double rifles formed only a very small part of their business, and that shotguns were their mainstay. In the case of Jeffery, Leonard seems to have been his main supplier. Fellow Melbournite, Wal Winfer (author of the "British Singe Shot Rifles" series of books) spent many hours going through Jeffery's records when thet were in the posession of Holland and Holland, came to the conclusion that Thomas Turner Jr. of 8 Fisher Street, Birmingham was his major finisher of rifles, including doubles, bolt actions and single shots.

But, gundealers like Jeffery were businessmen, and if Supplier A could not meet a delivery schedule, then Supplier B would get the order. Or maybe the Retailer was behind in his payments with Supplier A and had his credit cut off!

In other words, the trade was pretty fluid, and there are no hard and fast rules as to who made what! It is possible that a "Wheeler and Dealer" like Jeffery bought in parts from other trade gunmakers in bulk and sent them out to other trade makers for finishing, rather than outworker actioners, stockers, engravers etc.

Since Jeffery used a lot of Krupp barrels for his double rifles, it could be assumed that few were bought in as barreled actions, which would seem to excude Leonard as a major source. But, it ought also be recognised that the pattern of sourcing would change over different timelines.