During 1911, the NSW Government Railways realised that in order to meet growing traffic demand, new carriages were needed. Various proposals were evaluated until a design was established that would become the standard for the next 25 years. This design came to be known as the 72'6" cars.

The design was developed by Chief Mechanical Engineer E.E. Lucy, and the new carriages were initially coded TAM for the sleeper, CAM for the composite sleeper, TBC for the first-class sitting car, and TFX for the second-class sitting car.

The design was highly adaptable, leading to a large family of carriage codes and layouts. From their introduction, the 72’6” cars served the state’s principal long-distance and mail trains and even appeared on interstate expresses to Brisbane and Melbourne.

Their length and smooth-riding bogies provided improved comfort over earlier stock, while their corridor and compartment arrangements reflected the standards of the day. The series also proved versatile: in the 1940s, damaged vehicles such as TAM 907 and TBC 555 were rebuilt into new configurations like the MAM dormitory sleeper, extending their utility.