Thanks Bru,
I've just been watching fieldsport cymru on YouTube he mentioned series 5 was the first to have scope rails fitted but he also mention's by series 5 they got rid of the serrated tap loader, the grooves on rear of cylinder & a more straight trigger
My rifle has serrated tap loader, curved trigger, grooves on rear of cylinder & scope rail, possibly a late series 4 or very early series 5?