A change in the dial 21FA CLEAR
I noticed today that not all clear moulded GPO dials are the same
https://www.britishtelephones.com/dial1.htm says
The Dial No. 21CA (Colour) was made for the "700 Series telephones", but was "made obsolete in 1969 and superseded by the Dial, Automatic No. 21FA Clear".
The Dial No. 21FA (Clear) was "Introduced in June 1967 and an improved version in September 1971. The introduction coincided with the nationwide introduction of all figure numbering. This dial was also fitted to all factory refurbished telephones that had a Dials, Automatic No. 21CA."
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Looking at drawing DPL 2145, it looks like that in 20th March 1980 "sheet 3" was added to the drawing, with the "Alternative" Lipped design.
http://www.thgr.co.uk/ has a 24th Jan 1972 version of the drawing DPL 2145 which presumably is the "improved" 1971 version mentioned above.
This is Dial 21CA the Colour predecessor of the Clear Dial - Made of un plasticized vinyl chloride copolymer cobex 'F' grade at first, then later in Sept 1965 ABS was approved for this part
Extract from DIAL, AUTOMATIC NO. 21FA(CLEAR) (MARK1)
3/DPL/2145
DRG= DPL/2145
Moulded Dial seems to be Item 15, with lens Item 18
PDF / Image
Link
Type
Location
Reference
Name
Usage
Type
Equipment
DGM
G.P.O./D PART/DPL/
DPL 2145
Parts 1-/DPL/2145 (Plate Finger)
The coloured ancestor of the clear dial DPL/2018
Sheet 3 - Alternative Construction - 1980
cross section through the Dial for the original and alternative ( SHEET 3) designs
On the Left it can be seen that there is a countersunk hole for the securing screw, on the right a much larger area is countersunk.