Model by Alexander Crum Brown (1838-1922) of a half-twist mathematical surface, featuring a non-Euclidean so-called Klein bottle, c. 1900.
- 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.