STC TRIMPHONE PROTOTYPES
These pictures are of an STC prototype Trimphone, which is undated.  This is a prototype of the GPO Telephone No. 712 but is the number 66 the date, as the three hole casing was superseded by a single case fixing in 1966.

The first trial versions of the Trimphone (1965) were all two-tone grey.  The following year, two-tone blue, and green/brown were added.

The numbers on the base of the telephone below identify it as a Field Trial Trimphone:-

The numbers on the base are identified as follows:-

First Line
66-LAU-60
This is an STC code that identifies it as a 712 Mark 1 or 2.

AAB
The first letter can be 'A' or 'G'. It gives the climate rating of the phone.
A - UK use
G - is for tropical climates.

The second letter may refer to the type of dial.  In which case:-
B - UK Letters and Numbers.
G - North American with letters and numbers and the word "Operator" printed above the 0.

The third letter is for the colour:-
A - Grey-white.
B - Grey-blue.
C - Grey-green.

Second Line
S(W)2091 - Is the GPO specification number which identifies the telephone as a Mark II.

Third line
712L  - Is the GPO designation number with the L denoting that it has a dial with Letters.
TCE/67/2 - TCE being the GPO factory code for STC at Enniskillen, N. Ireland, made in 1967 and a Mark II.

Click here for GPO Trimphone history

STC prototype telephones

 

 
 
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Last revised: October 11, 2023

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