14/CSR would make it a 'Model 14 CSR' but that would also seem to make it the AJS version, not a Matchless (G2 CSR) although they are practically identical, the frame of course could be Matchless (what is the frame number?) and the registration document (maybe you do not have that if you do not know the numbers?) could also show it as a Matchless as the parts would be interchangeable between both AJS and Matchless versions.
The fact that there is no year code included in the engine number suggests that it is after 1963, the 14 CSR was made from 1962-66, so I expect it is one of the '64-'66 models?
Unfortunately these 'Lightweight model' machines are not particularly sought-after, and so will not be particularly valuable.