140 cars were built, divided equally between the two suppliers, in Britain by both Brush Traction and Metropolitan Amalgamated Railway Carriage and Wagon Company, with the remaining 280 built in France by Les Ateliers de Construction du Nord de la France.

This proved to be unreliable and was quickly modified to a hand-operated system, with balancing weights.

The hand-operated doors could be opened by passengers whilst a train was in motion.

This potentially dangerous system remained in use on some District line trains until the late 1950s.

Following their withdrawal (by the mid-1940s) all other remaining District line trains with hand-operated doors were designated as H Stock.