The ZA9 is a beam tetrode with a 10 Watt anode dissipation and a 200 mA heater for series chain use. The 5B/104D is equivalent.
The KB/FE identifies this valve as being made to specification K1001 or K1006, the B denotes qualification by a UK authority and the FE identifies the maker as STC, Oldway (Additional to Paignton factory 'F').
The lettering on the reverse is the CV9994 designation.
Little can be seen of the inner construction apart from a flattened cathode tube and that the insulated coiled heater wire passes through the cathode four times.
The wide glass tube envelope is 29 mm in diameter and, excluding the IO base pins, is 69 mm tall.
References: Data-sheet. Type ZA9 was first introduced in 1965. See also1965 adverts.
