51907 is a Driving Motor Brake vehicle built at British Railways’ own Derby works in 1960. Following experience gained with the first batch of railcars built to a lightweight design from aluminium and completed in 1954/55 Derby Works developed a range of low density sets to a roughly similar design but with steel, rather than aluminium carriage ends to improve strength.
A large number of what became known as the Class 108 vehicles were built and 51907 was one of the final batch of 29 sets, which were different to the rest in that they had the large headcode box on the roof to house the four-character headcode box.
Each power car had two Leyland 150bhp 680 engines with standard mechanical drive and weighed only 29 tons, despite providing seating for 52 people and accommodation for the guard and luggage.