We have different memories of our O level grades because the system changed several times between 1951-75 and varied somewhat between the different exam boards. Until 75 all O levels were pass/fail and only pass was recorded on the certificate against the subject. However, usually the actual grade was given separately to the student. % were given until 1960, then for several years grades 1-9 with 1-6 being passes, then from about 64, letters A-G with A-E being passes were used until1975. At least one board for some reason no one seems to know used A,C,E as passes and F, H as fails from the late 60s to 75.