This military valve is electrically equivalent to an 807. It could therefore be used at audio or for RF power generation up to 30 MHz.
The valve employs a flat cathode, two wire inner grids and beam forming plates, within a carbonised oval anode cylinder.
The classic envelope is 48 mm in diameter, and excluding the UX5 base pins is 124 mm tall.
References: Datasheet & 1040.