Got some answers back from Glasgow University who hold the archives for Army Navy CSL stock/sale books . My rifle, originally 303 was sold on the 17th September 1899 to a Capt. Baynes. The 4 digit alpha numeric number is the manufacturers number from BSA.

As advise in an earlier post, the rifle has been re-barrelled to 303/25. I located some dies (Simplex) and have started to develop loads and I can advise that it is an absolute joy to shoot. Minor issue is that the original sights were placed back on the new barrel and, unsurprisingly, it shoots high given the faster lighter projectile. I can live with this but need to convince a Fallow Deer to stand still and be close enough not to worry about the rising trajectory!

Finally, I managed to find an original leather Winchester sling (off an 1885 Highwall) in my collection that has the appropriate hook/sling swivels for the sling studs on the rifle. Not quite correct but period correct enough for the 303/25 Lee Speed.

Cheers