One of four Bakelite office telephones for inter-office communication, manufactured by ATM. When combined with a wood flour filler, phenol formaldehyde, known by its trade name 'Bakelite' after its inventor Leo Baekeland, forms a useful mouldable plastic, with very good electrical insulating properties. It was the first plastic to be used for making radios, and was ideal for the Art Deco-style designs of the 1920s and 1930s.