GPO 312L telephone, Johan Christian Bjerknes and Jean Heiberg, 1954

This beautiful GPO 312L telephone (refer image below) is currently on display in the museum for just a few weeks more, as part of our exhibition Why Plastics? I love it because it reminds me of my own 312, although mine is black in colour and made of bakelite (phenol formaldehyde).

AIBDC : 008939
Image credit: Katherine Pell

The 300 series was first introduced by the General Post Office in 1937, providing their first telephone with an integral bell in a one-piece moulded case. It offered two main advantages over its predecessors: it was more cost effective to make (one case compared to a variety of mouldings) and easier to fit (reducing the possibility for errors).

Bjerknes’ and Heiberg’s table telephone design.
Image credit: https://www.nasjonalmuseet.no/en/collection/object/OK-17526

The design was based on an earlier model released by Ericsson in 1932, designed by technician Johan Christian Bjerknes and artist Jean Heiberg (refer image above), but the arrangement of the internal componentry was all new. Available in black (phenol formaldehyde), Chinese lacquer red, ivory and jade green (all urea formaldehyde), there were seven main versions of the phone produced, the 312 being made available from 1949.

The pull-out drawer.
Image credit: Katherine Pell

MoDiP’s example has a one key plunger, a pull-out drawer with an envelope in cellulose nitrate (providing convenient storage for a list of dialling codes) and a No.164 handset. Underneath it is stamped 312L S54/3A on the base, denoting that this model was the Mark 3A, made by Siemens Brothers in 1954, the L suffix referring to the chrome dial having both letters and figures.

The markings on the base.
Image credit: Katherine Pell

A design classic, the popular 300 series telephones were in production for the BPO for about twenty years before being superseded by the 700 series in the 1960s. This new style was considered more modern, it was available in a larger variety of colours and was made from a different plastics material with greater impact strength properties (ABS - acrylonitrile butadiene styrene).  MoDiP has several examples of these phones too (plus lots of other designs) which can all be viewed in the museum on request.  

Why Plastics? is on display in the museum until 2nd September, 2022.

Katherine Pell
Collections Officer

References:

Cook, P. and Slessor, C. (1998). An Illustrated Guide to Bakelite Collectables. Quantum Books: London.

Emmerson, A. (1986). Old Telephones. Shire Publications Ltd: Bucks.

Pearce, C.A.R. (1938). The New Combined Hand Microtelephone and Bellset. The Post Office Electrical Engineer’s Journal. Vol 31. April 1938. pp 1-4 (online). http://www.samhallas.co.uk/repository/documents/poeej_new_combined_microtelephone.pdf Accessed 31 December 2021. 

https://telephonecollecting.org/Bobs%20phones/index.htm

https://www.britishtelephones.com/t312.htm

https://www.ericsson.com/en/about-us/history/products/the-telephones/the-bakelite-telephone-1931

https://www.nasjonalmuseet.no/en/collection/object/OK-17526