Southern Railway inherited a variety of coach stock that had been used by other railway companies pre-grouping.  Furthermore, Southern Railway continued to build new coaches to the  design of the three largest companies. The Maunsell carriage was  intended to be the standard carriage design for use across the Southern  Railway lines, incorporating the best features of each of the former  companies' designs. Maunsell Coaches were constructed between 1925 and  1936 at Eastleigh, with 1200 being built.

The standard  coach design was 59ft long and made from wood with steel sheeting. One  feature of the coaches was the low window placement which while less of  an issue when seated, meant that whilst stood up it was difficult to see outside the coach without ducking. In 1929 this feature was amended,  resulting in the introduction of 'high window' coaches, although on  corridor coaches the low windows remained on the compartment side of the coach. In operation, coaches were grouper together to form sets. The  intention was that coaches would remain in these sets for long  durations, with the set numbers appearing at the brake end of the set.  139 sets were created with loose stock being used to supplement the sets on busier trains.

In August 1925, construction began on  six First Class Dining Saloons for the Western Section. The first of a  batch of twenty-six such vehicles under Diagram 2651, they were intended for the London-Bournemouth, London-Portsmouth and London-Exeter  services and were of the low-windowed design. Seating twenty four  passengers in four seating bays at one end and the kitchen, pantry,  service vestibule and side corridor at the other, a set of double  loading doors opened into the vestibule, while the passengers accessed  the Restaurant from the gangways at either end.

Four  further low windowed Dining Saloons were completed between July and  December 1929, intended for the inter-regional through sets and in  May/June 1930, ten further Dining Saloons entered service, under Order  464, on West Country workings.