The class 'AB' was a fixed wheel sitting carriage with combined compartments for First Class and Second Class passengers. The First Class compartments were wider, allowing for more legroom.
Vehicles in this group were built between 1859 and 1887. Ten more carriages were converted to AB in 1892. The class numbers were 1 to 157.
Between 1888 and 1904, the class was progressively converted for other uses. Classes recoded to were: _B__, _BH_,TBO_, WMA_ and _WS_. Only ten were scrapped between 1890 and 1900. Car AB 118 was placed into excursion traffic as ABH 118 about 1900.
During the 1910 recoding the class letters 'AB' were altered to _XY_. Other conversions saw cars go to XYH_ and _YH_.
The car ABH 118 was relettered to XYH_ 15 in the 1910 recoding. It was removed from service in 1913.