The "PL" group were built on the underframes of swing door cars made surplus when the bodies were placed onto electric motor car underframes. These underframes were originally from carriages of 45' and 50' in length built 1886 - 1902. The underframes were lengthened with splices when the cars were modified to increase passenger seating.
The second class excursion cars were coded BPL: B - Second Class, P - passageway (centre aisle down the car), L - Lavatory fitted.
There were fifty five BPL carriages built between 1919 and 1921. The number group was eventually 1 - 126. There were conversions from the First Class cars, APL_.
In 1932/33, fifteen APL cars were converted to BPL. These cars were later recoded and renumbered back to APL. When the fleet of APL cars were reclassified to BPL in the mid 1960's, the APL cars previously coded BPL were not given their old "BPL" number back. This led to the same BPL number being occupied by different cars thirty years later.
They were affectionately known as "Bouncing Passenger Lounges" and were removed from service by the early 1980's.