![](https://coimages.sciencemuseumgroup.org.uk/74/294/medium_thumbnail_1990_0459__0002_.jpg)
Spiral scale of chords in the form of a circular slide rule
Spiral scale of chords in the form of a circular slide rule, with celluloid cursor in metal mount, cardboard 4 13/16-inch diameter with descriptive leaflet
Spiral scale of chords in the form of a circular slide rule, with celluloid cursor in metal mount, cardboard 4 13/16-inch diameter with descriptive leaflet