In the 1940s the C, D and E stocks were reclassified as "H Stock" (signifying hand-operated doors), along with other pre-1938 District Line rolling stock that had not been converted to have air-operated doors.
In the 1940s, the C, D, and E stocks were categorized as "H Stock" (signifying manually operated doors), alongside other pre-1938 District Line rolling stock that had not been converted to have air-operated doors.