IBM 72 typewriter, c 1961.
© Science Museum / Science & Society Picture Library
The IBM 'golf ball' typewriter revolutionised the 1960s office. For the first time a single machine offered interchangeable typefaces, a carbon ribbon, an electric drive, a small footprint and weighed only 14 kg. The secret is in the nickel-plated plastic type head, which is positioned for each stroke by a mechanism that tilts and rotates it to bring the required character to the front, before striking it against the ribbon and moving it on one space. Later variants gave proportional spacing, with high quality print.