The original version of this tube, the 144-9-T, used 4000 volts on the anode, and was introduced in 1938. In 1939 the 14AP4 was introduced, which had an "accelerator" element, allowing a total of 8000 volts of anode voltage. After World War Two, DuMont introduced the K1003P4, which was designed as a replacement for the earlier tubes.
Electronics, July 1938
Here are some more detailed photos
Courtesy of Mike Schultz
The gun attached to the stem
RF heating of the getter