"The way in which yesterday’s science so often becomes today’s recreation does not make it any less scientific. Indeed, much scientific, and other, knowledge is absorbed consciously or unconsciously through play."[Gerard L’E. Turner, Presidential Address: ‘Scientific Toys’, British Journal for the History of Science, Vol. 20 (1987), pp. 377-398, here p.384]. In his 1987 presidential address about ‘Scientific Toys’, Gerard L’Estrange Turner wrote of the importance of ‘Homo Ludens’ when “considering how human beings acquire knowledge” (Turner, 1987, p. 377). Picking up on his study of philosophical instruments that passed into recreational use in the 19th century and became toys in the 20th century, this paper suggests that thinking of scientific instruments as playthings opens them up to the kind of research that bridges academic and museological concerns. I begin by arguing that the attention to technology and materials during play leads a consideration of scientific instruments into the realm of playthings [cf. Walter Benjamin,‘Toys and Play: Marginal Notes on a Monumental Work’, in eds. Michael W. Jennings, Marcus Bullock, Howard Eiland and Gary Smith, trans. Rodney Livingston et al. Walter Benjamin: Selected Writings, Vol. 2, Part 2, 1927–1930 (Cambridge & London, 2005), pp.117-21]. I then explain how regarding instruments as playthings allows for a phenomenological/ecological approach to artefacts that takes into account their varying roles and meanings. This will allow me to introduce the notion of ‘historical affordance’ to relate the evolution in what an instrument offers to perception and understanding. After fleshing out this methodology, I sketch briefly its application in three case studies: the gyroscope, the radiometer and the string surface model. These will demonstrate how thinking of the artefacts as playthings offers scope for ‘tuning in’ to the instruments whose instability and mobility are put forward.