In message , Jim Brittin
writes
The increments were whatever applied at the time, probably was 3d at
the time of decimalisation.

Penny increments show in the LT Museum's 1948 photo.

View at http://makeashorterlink.com/?N3F63287A

Vaguely remember seeing an odd machine somewhere that wasn't just an
ordinary single, may have been a child single.

Oh yes, those are the ones, thanks. The tickets were green cardboard
when I first used them but soon changed to yellow with a magnetic
coating on the back that would operate the new barriers.

--
Michael Parry
'The Truth Shall Make Ye Fret'
(Terry Pratchett, The Truth)