The 75 is a double diode triode for superhet AM detection, AGC detection and first audio voltage amplifier.
This exhibit carries the paper label stating that this has passed a Special Export Test and is Quality Approved.
The 75 has a 6.3 Volt heater and a UX6 base. The 2A6 has the same rating and base but a 2.5 Volt heater. The 6B6G is also the same basic valve but has an IO base.
The triode at the top with the two diodes below in a screening box. The diode anodes are just vertical rods.
The triode anode is blackened for good heat dispersal and the two halves are stitched together.
The classic envelope is 38 mm in diameter, and excluding the UX6 base pins is 99 mm tall.
Reference: Data-sheet. Type 75 was first introduced in 1937. See also1937 adverts.
