The 4328A is a low power amplifier pentode from STC. It was probably designed for use in telephone repeaters but the data does not specify a design purpose.
The Type is also printed on the reverse. The 4 prefix indicates a UK STC made valve the 328A would be an American product from ITT if it existed.
The outer woven screen with cylindrical anode within. Three wire grids and an oxide coated cathode tube.
The top mica components with the control grid heat radiating fins and connection to the top cap.
The classic envelope is 38 mm in diameter and, excluding the UX6 base pins, is 108 mm tall.