Circular slide rule: "Dialor for calculation of vibration level for random noise of uniform spectral density"

Rectangular plastic slide-chart made by Perrygraf for complimentary distribution by IBM Federal Systems Division

"Boucher" circular calculator, by Stanley, Great Turnstile, London "Boucher" circular calculator, by Stanley, (glass 1880-1890

Fearnley's patent Universal calculator, circular slide rule with cardboard scale in fitted mahogany case, unsigned, British,1880-1900. Used at the University Observatory, Cambridge, at Madingley Road, Cambridge, England. Fearnley's patent Universal calculator

Circular slide rule, brass, 5" diameter, in case, made by Haas and Hurter, of London Circular slide rule

Palmer's Computing Scale, improved by Fuller, (a circular logarithmic slide rule, with numerous gauge points); on reverse side "Fuller's Time Telegraph" Palmer's Computing Scale 1846-1880

Fowler long scale calculator, circular slide rule with carrying case and instruction booklet, 1920-40. Fowler long scale calculator 1920-1940

Circular slide rule, Fowler "Magnum" long-scale calculator, in fitted case with instruction booklet by Harold Fowler Circular slide rule

The "Small" Pocket Calculator, a circular slide rule patented 1918, made by G. Small, Boston, in leather pouch The "Small" Pocket Calculator

Halden "Calculex" patent circular slide rule (5 inches diameter) in case, c. 1906 Halden "Calculex" patent circular slide rule (5 inches diameter) in case 1904-1907

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

Circular slide rule (two cardboard discs with radial transparent plastic cursor) by General Industrial Co.1788 Montrose, Chicago 13,Illinois, also marked Slide Chart Corp., 1959, Perrygraf, Marywood, Illinois Circular slide rule (two cardboard discs with radial transparent plastic cursor) by General Industrial Co.1788 Montrose 1959-1960

Circular slide rule with lockable cursor arm, plastic, in envelope with instructions: " Eckel dial rule", Engineers' Model, made by Lithocalculator Company, Calfornia Circular slide rule with lockable cursor arm

German circular slide-rule, type KRS 40, No.1246, 17 1/2 inches diameter, fitted in a metal case 18 1/2 x 20 inches German circular slide-rule

Circular slide rule by Pickett, metal and plastic, in leather pouch with instruction booklet Circular slide rule by Pickett

Circular slide rule by Fowler and Co., Manchester, model RX, double faced, serial no. 7384, with descriptive leaflet in metal case Circular slide rule by Fowler and Co.