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.
During the 1940s, the C, D, and E stocks were renamed "H Stock," which indicated hand-operated doors. This reclassification also included other pre-1938 District Line rolling stock without air-operated doors.