A model of the ex-GWR suburban type brake composite coach used as the basic coach for many local and branch line trains.
Often a branch line or mainline local stopping train would be formed of two of these coaches coupled together, sometimes permanently, the formation being known as a B set.
Trains were often formed of basic units formed by a small number of coaches, with a full train comprising several units. For convenience a train formation book was issued and each unit given a letter dscription.
The GWR latterly used the letter B to describe a two-coach train formed of two suburban brake composite coaches, this was the basic train which provided accomodation for first and second class passengers on many local and branchline trains. The two coaches were coupled together with the guards' vans outermost.