The University of Glasgow has Army & Navy Co-operative gun stock books up to c. 1942
https://www.gla.ac.uk/media/Media_803949_smxx.pdf
Webley & Scott made many of the C.S.L. shotguns but unfortunately limited records exist
https://www.armsresearch.co.uk/The%...chive/Webley%20and%20Scott%20Archive.htm
There should be a Birmingham date of proof code on the barrel flats