Lincoln Jefferies was an 'assembler' of gun components (and a retailer). His shotguns has a very 'good' name.

There was a similar question in 'Shooting Times' in 2012 - but it was regardimg a shotgun, not a sporterised SMLE.

The answer being :

Lincoln Jeffries (1847? 1932) was a prominent Birmingham gunmaker best known for designing the tap loading underlever air rifle subsequently built by BSA.

He occupied various premises in Whittall Street and Steelhouse Lane in the heart of the city?s gun quarter.

Less memorably, he was also involved in litigation with William Ford over a patent, and was forced to concede that Ford had bored his guns that won a gold medal in The Field trials of 1879.

Jeffries was something of an inventor, with a dozen patents to his name.

Though he was a gunmaker in the true sense of the word, your gun will have passed through many pairs of hands, as he would have had all the specialised functions of manufacture performed by outworkers.