Re: When was the No 12 dial introduced?
Difficult to be precise about phasing I think as there were a number of different suppliers of phones to the GPO and the availability of raw materials for tooling and manufacture would have been an issue at the time. However, it's probably safe to assume that new installations would have had the new dial by the early fifties. It's also worth remembering that a new (or refurbished) dial would have been retro-fitted to older phones if a dial failed in use. It's relatively unusual to come across a phone from this era where all the parts have corresponding date stamps.
Alan
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