|Number built:||129 cars (43 3-car sets)|
|Builder:||Metro-Cammell / Birmingham Railway Carriage & Wagon Company|
|Engine:||4 BTH traction motors (750v DC third rail)|
|Power:||540 hp (403 kW)|
|Formation:||(Original) Driving Motor Brake Standard (DMBS)+
Trailer Composite (TC)+Driving Trailer Standard (DTS)
(Modified) DMBS+Trailer Standard (TS)+DTS
In the 1970s the stock was modified to have central end doors to comply with Department of Transport regulations for stock which operates in single track tunnels (to allow for the exiting of passengers in an emergency if the side doors cannot be used) . They also had their first class provision removed to become fully standard class.
After a long career the Class 503 was finally withdrawn in 1985 when they were replaced by the 507s and 508s though one set was preserved and kept for special services until 1988. The preserved set is now at the Electric Railway Museum and was from the 1938 Stock batch, it is one of only two pre-war EMUs still in existence in it's original condition.
|DMBS 28690 at the Electric Railway Museum|
|The preserved set wears LMS maroon livery|
 Colin J. Marsden, DMU and EMU Recognition Guide (Ian Allan, 2013) p, 381
 R.L. Vickers, EC Electric Trains and Locomotives in the British Isles (David & Charles, 1986) p. 74
 Brian Haresnape & Alec Swain, Third Rail DC Electric Multiple Units (Ian Allan, 1989) p. 28