SMLE trade rifle (need some guru help)

[SR(b)]

So sorry to bump such an old post, but I am the owner of a rifle with a serial number only 48 greater than Cdn303's example.

These images are originally from the site of the seller I purchased the rifle from a number of years ago, and helpfully show the pertinent areas in question. As you can see, it shares the peculiarity of having a BSA commercial marking, with a cipher added separately, but with no year of manufacture or model designation. It has also found it's way through AG Parker's and Fulton's, ending up in a SR(b) target rifle configuration.