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
Example of G. Charpentier's Calculimetre
Circular slide rule in pocket watch case by Scientific Publishing Company
1900-1920
Circular slide rule for calculation in simple interest
Circular slide rule by Paul Pouech ("Cercle complet" model)
Circular slide rule
1962
Circular slide rule for surveying calculations: "Cox's stadia computer"
Acoustic and Solar Circular Slide Rule, 1942
1942
Circular slide rule, c 1870.
1870-1875
Circular slide rule in brass
1878-1882
Midget circular slide rule by Dietzgen
1955
Circular slide rule
1955
"Automatic calculator"
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
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
Circular plastic slide rule
Circular slide rule
Circular metal slide rule by Muchall & Co.
Brass circular slide rule 30cm diameter
1818-1820
Bakelite "Celercertus" rotary slide rule (Brit patent no.413451)
Circular slide rule
Halden's 'Calculex'
Circular slide rule by Fowler and Co.
Circular slide rule
Circular slide rule by Pickett
Circular slide rule
The "Small" Pocket Calculator
Circular slide rule
Fowler long scale calculator
1920-1940
Halden "Calculex" patent circular slide rule
1904-1907
Circular slide rule
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
Circular slide rule with lockable cursor arm
circa 1955
Halden "Calculex" patent circular slide rule (5 inches diameter) in case
1904-1907