There were thirteen ACD cars, numbered 1 - 13. They entered service between 1919 and 1921.
They were converted from _AC_ steam hauled cars.
At the time suburban carriages catered for "First" or "Second" class and were coded accordingly.
With the introduction of the 1921 recoding, motor cars were designated as "second" class and trailer cars _D__ and _T__ were "first" class.
The ACD class was recoded to _D__ 1 - 13 between 1921 and 1924.