Late 1930's and onward Cords have a suffix letter in the description.
Below is an explanation of what the suffix letter means.
Not all are included as only the suffixes up to 1940 could be located.

Click here for the Cords, Instrument page

Letter Type Insulation Purpose
A Plaited, tinsel conductors. Textile Telephone instruments in dry situations (except for instruments shown under D and G).
B Plaited, tinsel conductors. Waterproof.
Rubber Ditto in damp situations.
C As for B, but with stronger outer covering.
Rubber Linemen's and other portable telephones.
D As for A, but with better flexibility.
Textile Microtelephones and recs.
E Stranded, copper conductors.
Impregnated textile. Flex. intl. connections of instruments.
F Braided overall, copper conductors and strong outer covering. Rubber Testing appliances and telegraph. instruments etc.
FSI As for F except that 1 conductor is copper screened.    
G Braided overall, copper conductors. Impregnated textile. House and intercom. telephones, etc.
GS 2-pairs. As for G except that 2-pairs are copper screened.   Loudspeaker instruments.
H Braided overall, copper conductors.
Rubber Combined bell-sets and telephones, etc.
J Stranded, tinsel conductors.
Textile Wiper Cords
K Cab tyre, tinsel conductors. Rubber Microtelephones and receivers in exposed situations (street boxes ; Police, Fire, etc.).
KB Cab tyre, braided overall, tinsel conductors.
Rubber Alternative to K type for special cases (under carpets, etc.)
L Cab tyre, copper conductors and high insulation.
Rubber Mains supply connections of tele-printers, etc.
M Cab tyre, copper conductors. Rubber Telephone instruments, in exposed situations (except for instruments shewn under K).
AA Plaited, tinsel conductors. P.V.C. Telephone instruments


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Last revised: August 14, 2023