The early electric trains used on the District line reflect American train styling and the influence of American financier Charles Tyson Yerkes. This carriage retains a raised section in the roof that was known as a clerestory and provided ventilation for the Passengers. In 1938, the carriage was converted. The sliding doors were changed to air-operated doors controlled by push button. This allowed individual pairs of doors to be opened without every door in the carriage needlessly opening and letting in the cold, but this design proved to be difficult to maintain so was eventually discontinued.