All telephones are available to buy by mail order
As a guide,
Type 8 dial Rarely seen. Has a small dial centre, and 4 screw terminals on the back. Otherwise basically similar to the type 10.
The type 10 dial was used with most British manufactured telephones from 1923 to around 1951/2. These include candlestick, wood wall phones, 200 series, and 300 series. Early examples had either a small or large dial centre and a brass or copper finger plate finished in black. Later by the early '30's they all had large dial centres and stainless steel finger plates.
The Type 12 dial was used on many British made telephones from 1951/2.
These include 200 series; 300 series and early 700 series telephones
Both type 10 and 12 were made with variations for specific purposes.
Dial type 17LA Miniaturised dial fitted to test telephone type 280. Picture to follow.
The type 24c dial was specific to Automatic Telephones and Electric (and
their subsidiaries) manufactured telephones. Some had chrome plated finger
plates, but most had a brass plate finished in black. A variation of the 24c is often
seen fitted to an Indian made or sourced telephone.
The type 21 dial in various forms was used from about 1960 in most of the GPO
and BT dial telephones until the push button keypad took over.
There were large numbers of type 21 dials fitted with a chrome (actually
stainless steel) finger plate. They were often used where a more robust dial was
deemed necessary. Interestingly these are described on an "advice" web
site as fake. They are not!
Most foreign dials are specific to the manufacturer of the telephone, but some early Danish telephone dials were British made and based on a type 8 or 10 dial.