The 75 is a double diode triode for superhet AM detection, AGC detection and first audio voltage amplifier.
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 Ken-Rad name is pressed into the Bakelite base.
The triode section is at the top with the two diodes below. One diode anode is the bright box and the other is formed by the rods within the box.
The classic envelope is 38 mm in diameter, and excluding the UX6 base pins is 94 mm tall.
Reference: Data-sheet. Type 75 was first introduced in 1937. See also1937 adverts.
