Was there ever a "Telephone Set 'E'", I wonder? (Or 'G' 'I' and 'K', for that matter?)
Presumably only development models that never made it into service.
'A' existed, and was very heavy (56 lb?) with wet Leclanche cells.
'B' also existed, as far as I'm aware.
'C' was the first real 'portable' (as opposed to 'transportable') telephone.
'D' began life as a commercial Siemens telephone, and 'Marks' I through V* exist.
'E' ?
'F' exists as Mk.I (cast alloy case with hinged lid), Mk.II, Mk.II* with buzzer replaced by induction coil after buzzer calling was obsolete.
'G' ?
'H' exists as Mk.1 and Mk.II in Tele-F cast cases, and Mk.III in Tele-L style pressed steel cases. "Sound powered" with dynamic inserts for microphone and earpiece, magneto call/bell, used for short distances (ranges and coastal defence installations)
'I' ?
'J' Fully tropicalised version based on Telephone Set 'L'
'K' ?
'L' Standard late WW2 linemans telephone.
'M' ? There's an STC Field Telephone 'M' that I thought was commercial only, but have since discovered versions with both Air Ministry and Army stores codes. Takes a 4.5V flat lantern battery (3LR12?) and is buzzer call only.
'N, O, P, Q, R & S' ?
'T' Supposedly to go with the Switchboard, Magneto, 10 Line (W.D.) and appears (as a 'ghost' image) in the early manual for the switchboard. It apparently existed but was not proceeded with, being twice the size of the Telephone Set 'J' that was used instead.
There are also Ericsson 'N1845' telephones that used Telephone Set 'L' and 'J' case components but were painted brown. These were rugged instruments for the civilian market and offered a variety of features (CB or local battery, magneto signalling, and an optional rotary dial).
See:
http://www.britishtelephones.com/ericsson/n1845.htm
N1844A was the Telephone Set 'J'.
If you can find the battery adapter for two 'D' cells, it's very useful!
Chris.