Having spent many years researching and collecting phones in Australia, I thought that the following phone history may be of interest in this discussion. All information is taken from technical documentation of the time and I have examples of most of the phones that I mention.
The first phone with both a bakelite handset and case was made by Automatic Electric (USA) in 1925 and was called the 'Monophone'. (Bell/Western Electric claim to have invented the bakelite handset in 1925 but did not make a plastic, not bakelite, case phone until the late 1930s.) From this concept the British company Siemens Brothers developed their bakelite phone called the 'Neophone' between 1927 and 1929. There were two table versions of the 'Neophone' and a wall version. The British Post Office (GPO) adopted a modified version of the 'Neophone' as the Handset Telephone No. 162 in 1929 as a replacement for the metal 'candlestick' type. Initially this had a metal base but shortly afterwards a bakelite base with a lead weight was made. This base did not have a pull-out number index. The Tele 162 did not have an internal bell but used the wood case Bellset No.1 which also contained a 2mF capacitor and the induction coil. The handset was a No.164 with a 1L receiver and No.13 carbon transmitter. There was an anti-sidetone transformer fitted in the case of the Tele 162 to compensate for the improved efficiency of the handset which otherwise had a tendency to 'howl' due to feedback under certain conditions. By 1932 a bakelite case No.25 bellset was made which could be fitted under the Tele 162 or mounted on a wall. About the same time the pull-out number index base was available as an option. The Tele 162 was made in bakelite coloured either black or brown and also in thermoplastic coloured ivory/cream, red or green. Gold was also available by painting a black phone. The Tele 162 was wired for either Central Battery (CB) or automatic (dial) working.
Other British companies such as ATM and GEC made Tele 162. GEC also made a similar phone with a No.164 handset but an internal bell, capacitor and anti-sidetone induction coil which was called the 'GECophone'. The GECophone was available in black, brown and ivory. British Ericsson (later Ericsson Telephones Limited - ETL) made a phone that was similar to the 'GECophone'. Siemens Brothers continued to produce the 'Neophone' as well as the Tele 162. One table version of the 'Neophone' had a detachable Bakelite case bellset and the other had a one piece case with a metal base that mounted a bell, capacitor and anti-sidetone induction coil.
The Australian Postmaster General's Department (PMG) bought limited quantities of the Tele 162 in 1931 but designated it the '566A' (automatic) or '566C' (CB). The bulk of these were in black but some ivory, red and green were available at a premium. None of these phones had the pull-out number index base option. It was soon discovered that the red and green cases faded badly in strong light so they were withdrawn. At the same time the PMG allowed the local offices of Siemens Brothers, GEC and Ericsson to sell their phones (black only) to subscribers providing the phone was installed by a PMG tech and the subscriber took out a maintenance contract with the PMG. By 1933 the PMG had found that this maintenance was too costly due to having to stock four different sets of spares so all sales were stopped and the existing phones were acquired by the PMG. New 2000 type automatic exchanges were being installed to replace obsolete manual switchboards and thousands of 566A/162 phones were purchased from GEC. These were marked '162' and were usually installed with an attached No.25 bellset most of which were made by a smaller British company, Phoenix Telephones. A short three-conductor cable was fitted externally between the bellset and the top section of the phone. All new phones were marked with a gold PMG label on the base.
By 1936 AWA was making bakelite phones in Sydney which were marked 162 on the base but 566A on the circuit diagram pasted inside. AWA also made a magneto/local battery version that was marked 162LB on the base but 566M on the circuit diagram.
In 1937 an improved version, the Tele 232, was developed which had an anti-sidetone induction coil mounted in the top section in place of the anti-sidetone transformer of the 162. The Tele 232 came with a bellset permanently attached and the bellset had only a bell motor and 2mF capacitor. The connecting cable was fitted internally and passed through a small hole drilled in the cover of the bellset. The Tele 232 also had a wider handset cradle made from cellulose acetate that was not brittle and less prone to breaking than the cradle on the Tele 162. The PMG adopted the Tele 232 as the 232AT/232CB and reclassified the 566A/566C as the 162AT/162CB. Phones without an anti-sidetone induction coil were grouped as the 100 Series and phones with an anti-sidetone induction coil were grouped as the 200 Series.
In 1931 Ericsson in Sweden had released a new style of Bakelite phone which had a one piece case with a metal base. It had an internal chassis that mounted a bell, capacitor and anti-sidetone induction coil. British Ericsson tried to have a modified version this phone adopted by the GPO as an alternative to the Tele 162 but was rejected. Ericsson then resorted to political manoeuvring to have the decision reversed. After joint work between the GPO and British Ericsson a second modified version of the phone, designated the Tele 332, was accepted. This had a No.164 handset, retained the internal chassis layout but used the same bell motor and anti-sidetone induction coil as the Tele 232. The capacitor was a 2mF and a 0.1mF fitted in a single case. The Tele 332 had the pull-out number index base as an option. In 1938 the PMG accepted this phone as the 332AT/332CB but without the pull-out number index base option; a small bakelite cover was attached to the base plate to cover the slot in the case. The standard colour was black but small qualities in ivory, red and green were available and both the red and the green were fitted with the pull-out number index base option. Again the red and the green tended to fade badly but ivory could be installed for an extra cost. The 332AT was supplied by Ericsson (black and colours), ATM (black) and GEC (black only using sub-assemblies made by Ericsson). There was a Local Battery version but this had a different type number.
With the outbreak of WWII, supplies of phones from Britain were stopped. In 1941 the PMG designed a universal 300 Series phone that could be either auto, CB or Local Battery. (The Local Battery version had a small magneto generator designed by the PMG to fit in the same space as the dial in the auto version.) The design concept came from a 1938 design by Standard Telephones, parent company of STC (Aust). The new phone, the 300AT/300CB, used the same circuit and components as the 332AT/332CB but there was no internal chassis with components mounted on a heavy gauge steel base plate. The handset was a No.184 but wired as a No.164. The 300AT/CB was made in the PMG Workshops and also by AWA and STC (Aust). The only colour was black and there was no provision for a pull-out number index base. There was also a wall version of the 300 type. The 332 and the 300 were grouped as the 300 Series.
After 1946 supplies of 332 type phones resumed from Britain but the 300AT/CB was still made by AWA and STC (Aust). The 200 Series phones were deemed obsolete in 1951 and were progressively replaced with 300 Series phones.
During WWII a number of improvements were made to magnetic materials for telecommunications equipment and these were included in new receiver designs. The 2P was a more efficient receiver which replaced the 1L type and was fitted to all later Tele 232 and Tele 332 phones. Also a very sensitive rocking-armature receiver was developed for military use and post-war development by STC resulted in the 4T receiver in 1952. Using this receiver, GEC developed a new handset, the No.1, to replace the No.164 and an improved transmission circuit to work on lines up to 1,000 ohms resistance. These improved designs were added to a case similar to the Tele 332 but with a more rounded shape, to make the Model 1000 in 1956. (Ericsson used the same case with their own different handset design to produce their Model 1000 but this was still a 332 circuit with a No.13 transmitter and a 2P receiver. It could not work effectively on a 1,000 ohm line.) The GPO field tested the GEC Model 1000 as the Tele 700 but decided to change to a coloured ABS plastic case rather than bakelite. The circuit was the same as the Model 1000 but later included a regulator in the transmission circuit. This became the Tele 702 in 1959. The PMG did not use the Tele 702 but some companies such as Telephone Rentals (TR) used them in Australia on business PAX units they supplied.
The PMG were particularly interested in the GEC Model 1000 because it allowed for longer lines between the user and the exchange and for lighter gauge wire in cables. This phone was adopted as the 400AT/CB in 1959 but for unknown reasons it retained the 332/300 shape case. (PMG technical instructions for the 400AT dated 1958, show the Model 1000 case.) The 400 type was made in Britain by GEC (black) and Ericsson (black or ivory) using a small internal chassis design as the 332AT and locally in black only by AWA and STC (Aust) using the base plate mounting design of the 300AT.
In 1962 the PMG adopted a coloured plastic case version of the BTMC 'Assistant' as the 'Colorphone' 801AT which was then made by AWA and STC(Aust). The 801AT and the later 802AT replaced all 200 Series and 300 Series phones. Local battery versions of the 400 type were retained into the 1980s until all manual exchanges were replaced with automatic switches.
It can be difficult to sort out what are original phones now as the PMG rebuilt thousands of recovered phones in their workshops. Damaged phones were stripped down for parts and a mix of refurbished and new parts were used to make up what type of phone was required. Rebuild work was passed out to contractors like Blys Industries who made a lot of replacement spare parts and fitted them to refurbished phones. Many 162AT/CB were fitted with 232 type cradles or rewired to become 232AT/CB. British 332AT phones were rebuilt with locally made 300 type cases and 300AT phones were refitted with 400 series cases. Both were refitted with No.21 dials and 400 series handsets. In recent times dealers in old phones often made up phones from all sorts of parts and rewired them to work.