In 1957, Siemens Ediswan (the successor to Siemens Brothers and later to be bought by AEI) produced the Centenary Neophone, familiarly called the ‘Horseshoe Phone’. It was never adopted by the Post Office who were working on the 700 type telephone, but it was used by the Hull Telephone Company and abroad, as well as on private systems, such as the one above used in a hospital (‘Dial 424 for Cardiac Arrest’).
It was the precursor of the 700 type in many of its novel features. It came in various colours (including two tone, as here). It used a printed circuit board inside and sometimes featured a separate dial surround (but not here). However, it did use a traditional braid cord. A wall version was also produced.