Model by Alexander Crum Brown (1838-1922) of a half-twist mathematical surface, featuring a non-Euclidean so-called Klein bottle, c. 1900. Sources: Photo from the Science Museum, London, textual description courtesy of Klaus Hentschel. For more, see Klaus Hentschel (2014): Visual Cultures in Science, Technology and Medicine, pp. 96ff. and pl. XIV.

Illustrator and model-maker Roger Hayward (1899-1979) working on a model of the lunar surface for the Griffith Planetarium, 1934. Sources: Kevin Kidney (2009) Mr. Hayward's Moon Model. Photo from Keven Kidney's blog, textual description courtesy of Klaus Hentschel. For more, see Klaus Hentschel (2014): Visual Cultures in Science, Technology and Medicine, pp. 217-226.