The directly heated QU37 EHT rectifier looks to be a special quality version of the U37 that was designed for early post WWII television sets.
The peak inverse voltage on the diode was 15,000 Volts and the output voltage was 7,500 maximum. This is very low for a television receiver produced much after the late 1940s and a nine inch screen would be the maximum that could be supported.
The construction has a bell anode, fixed at one end and the emissive cylinder fixed at the other.
The double mica structure at the base holds the oxide coated coiled filament rigidly in position.
The thin glass tube envelope is 12 mm in diameter and, excluding the base wires, is 51 mm tall.
Reference: Data-sheet. Type QU37 was first introduced in 1952. See also1952 adverts.
