The 5A/102D is an audio output pentode for telephone repeater amplifiers. The old GPO code is POVT183.
The CV Type code is CV1724 and this also appears on the glass as an overprint.
The KB/F identifies this valve as being made to specification K1001 or K1006, the B denotes qualification by a UK authority and the F identifies the maker as STC, Paignton.
The seamed anode from the side.
The CV1724 designation.
The control grid copper supports are topped with a radiating fin. The heater is a single hairpin of insulated wire. At the top parts of all three grid windings are visible.
The top mica showing the U shaped grid cooling fin. Inside the anode the space is cylindrical.
The balloon envelope is 45 mm in diameter and, excluding the IO base pins, is 112 mm tall.
