The D63 is a double signal diode with separate cathodes. The old service code was ARDD3 and the later CV code was CV1301.
This exhibit has a plain envelope but a drain wire exists above the base cap indicating that some of the production was coated in metallic paint for extra screening.
One diode with an electrostatic screen behind.
Here the diode is on the left and the folded end of the screen is in the centre.
The Type designation is faintly present on the dome together with Patented and Made in England.
The classic envelope is 35 mm in diameter, and excluding the IO base pins is 76 mm tall.
References: Data-sheet, 1040 & 1043. Type D63 was first introduced in 1937. See also1937 adverts.
