The E2004 is an M-OV development sample of what became the U41 EHT rectifier.
The value of 15 kV appears written on the label with the letters P-L. The rated PIV of the production valve is 33 kV and 15 kV would be the maximum sine wave input.
The Serial number is 122 and the filament voltage is given on the label as 1.25 V. Inside it reads E1890.
Inside the bell anode can be seen the helical oxide coated filament.
The oxide coated filament as seen through the microscope.
The envelope blurs the image but the lumpy nature of the coating is clear.
The wide glass tube envelope is 29 mm in diameter and, excluding the IO base pins, is 86 mm tall.
References: Data-sheet & M-OV A and E Types. Type E2004 was first introduced in 1952. See also1952 adverts.
