When the BPO (British Post Office, later to be called the GPO) took over the privately owned National Telephone Company in 1912 they also took these telephones into their inventory and called them Tele No1. These are regarded as the first model of "GPO telephones"
Historical note, these antique phones were originally used in the UK by the National Telephone Company as their model Telephone No.15 which was in effect the NTC standard CB wall phone, introduced into service between 1881 and 1898.
The first truly standardised GPO telephone was the Tele 121 wall telephone. The mouthpiece was fixed to the front of the box and the switch hooks, holding the receiver on the left hand side. Below the mouthpiece was a dial. This made this antique GPO telephone a truly one-piece telephone.
The desk telephone that was produced during the same period was known as the Tele 150 (aka Candlestick Telephone). Together both of these GPO telephones were known as the "100 series" telephones.
This Tel. 150 desk telephone is easily recognisable from 1920's, 1930's British films of that era. It was the GPO's first standard desk telephone and is still a firm favourite for dedicated vintage telephone collectors.
Unlike the wall mounted 121 telephone of the same period the 150 series "candlestick telephone" was a two-piece telephone. The wooden "Bell Set" was separate to the main body of the telephone (as you can see in the video).
The first British GPO Bakelite telephones (introduced in 1929) were know as the 200 series telephones. The first model number was a Tele 162 and was relatively quickly replaced by a significantly improved Tele 232.
Again the "200 series telephones" were a two-piece telephone. The Bakelite "Bell Set" was again separate to the main body of the Bakelite telephone (please see the video for more details.
The first one-piece British GPO Bakelite telephones (to include the bell in the main body of the phone) were introduced in 1937 and were know as the 300 series telephones. They were issued at the same time as the earlier 200 series telephones and overlapped them for many years.
These "300 series Bakelite telephones" are probably the most iconic of all the British vintage telephones and are highly sought after (in good condition) by both telephone collectors and the general public with an eye for both style and function.
At the time the 706 telephones were a revolutionary telephone in the UK as they were made of modern plastic (rather than Bakelite) and so could easily be produced in colours other than Black. They featured heavily in the cult British TV series "The Avengers".
These 706 phones were available in Red, Ivory(cream), two tone green, concord blue (blue with a green tinge), topaz yellow, two tone grey and of course Black.