These were introduced around the 1970s, replacing the 33003 series. These were A5 size, coloured cover with white pages.
If you have any issues / variants not listed here, I would be pleased to hear from you.
Issue 5
September 1978
Issue 5
January 1980
Issue 4
February 1981
Each version clearly excludes the Class 126s - I haven't come across any equivalent for the Class 126!