The 4074A is a low power VHF transmitting double triode that would have been used in push pull with a common tuned anode coil connected across the twin top caps. The HT would be fed into the tank circuit centre tap. The base is ceramic for better resistance to heat and humidity.
Roy, an award winner audio amp designer, has used the 4074A and achieved good results at audio.
The twin triode sections with anodes connected to top caps.
The AM and Crown logo of the UK Air Ministry.
The etched lettering and the grid wire is visible under the top mica.
The classic envelope is 45 mm in diameter and, excluding the UX7 base pins, is 113 mm tall.