Fowler Magnum long-scale calculator
circa 1940
Circular slide rule in pocket-watch format
1880-1890
Circular slide rule
1918-1921
Lord's calculator
1837-1848
Circular slide rule, 1660-1680.
1660-1680
Circular slide rule and time zone scale
1947
Dixon's combined circular and spiral slide rule
Circular logarithmic slide rule by K. Emil Troger
Circular slide rule for calculation in simple interest
Example of G. Charpentier's Calculimetre
Circular slide rule in pocket watch case by Scientific Publishing Company
1900-1920
Circular slide rule by Paul Pouech ("Cercle complet" model)
Acoustic and Solar Circular Slide Rule, 1942
1942
Circular slide rule
1962
Circular slide rule for surveying calculations: "Cox's stadia computer"
Circular slide rule in brass
1878-1882
Circular slide rule, c 1870.
1870-1875
Midget circular slide rule by Dietzgen
1955
"Automatic calculator"
Circular slide rule
1955
Textile Calculator
circa 1900
A. E. W. circular slide rule
1948-1952
National Coal Board methane drainage pipe calculator with pouch
Type H circular textile calculator
1944
Herrmann's circular slide rule
Circular slide rule in pocket watch form
Rectangular plastic slide-chart made by Perrygraf for complimentary distribution by IBM Federal Systems Division
Circular slide rule: "Dialor for calculation of vibration level for random noise of uniform spectral density"
Circular plastic slide rule
Circular metal slide rule by Muchall & Co.
Circular slide rule
Brass circular slide rule 30cm diameter
1818-1820
Bakelite "Celercertus" rotary slide rule (Brit patent no.413451)
A.E.W. double sided circular slide rule
1948-1952
Circular slide rule, 6 1/2-inch diameter, in case
Circular No.101C dial slide rule with sythetic leather case and instructions
1965-70
"Boucher" circular calculator, by Stanley, (glass
1880-1890
Halden "Calculex" patent circular slide rule (5 inches diameter) in case
1904-1907
German circular slide-rule
Fearnley's patent Universal calculator
Circular slide rule
Circular slide rule
Fowler long scale calculator
1920-1940
The "Small" Pocket Calculator
Circular slide rule
Circular slide rule by Fowler and Co.
Circular slide rule by Pickett
Palmer's Computing Scale
1846-1880