Pocket Watch Style Logarithmic Calculators

This page contains circular slide rules. Many are very rare as the metal deterioriated faster than other materials over time. The more modern Russian KL-1 is still widely available. Thanks to the members of the UK Slide Rule Circle and of the Oughtred Society for most of the scans provided in this gallery.

Charpentier

Charpentier Calculimetre

Charpentier Calculimetre
Made in France - 5.92cm diameter
Front Scale: D, C ( W1, W2)
Back scale: L, S, T
Archive - Giovanni Breda Collection

Fowler

Halden, Joseph

Halden Calculex - Pocket Model	Halden Calculex - Pocket Model Made in Manchester, England by Joseph Halden 61mm diameter x 7.5mm Front scales: L, A [ B C(Square Root of B) ] Back scales: Degrees, A [ B(inverted), C(Cube Root of B) ] Scan donated by Paul Tarantolo, Houston, Texas
Halden Calculex - Desk Model	Halden Calculex - Desk Model Made in Manchester, England by Joseph Halden 126mm diameter x 15mm Front scales: L, A, [ B, C(Square Root of B) ] Back scales: Degrees, A [ B(inverted), C(Cube Root of B) ] Scan donated by Paul Tarantolo, Houston, Texas

Henri Chatelain.

H. C. Calculigraphe (Calculating Circle) Boucher's System

H.C. Calculigraphe (Calculating Circle) Boucher's System
Made in Paris, France by Henri Chatelain, c.1878
52.5mm diameter x 17.5mm
Front scales: L, Cube Root(3 Turns)
Back scales: S, C, Square Root(2 Turns)
Scan donated by Paul Tarantolo, Houston, Texas

Instructions 2.8Mb

K&E Pocket Calculator

K&E 4018 Pocket Calculator (Circular Mannhiem)

K&E 4018 Pocket Calculator sn 548 - c1913
Made in USA, Mfg by K&E, Designed by George Lange, US Pat# 1,012,660, Dec 1911
Front Scale: (C, D)
Back scale: Tangents, Log, (Sines)
Note: Scales are: Stationary (Revolving)
Archive - Photo by Elliot Pearce Family - Original owner, James A. Pearce was a railroad civil engineer and WWI veteran.

Lord's Calculator

Lord's Calculator - (R. Waddington)	Lord's Calculator - (R. Waddington) Made in Coventry, England by R. Waddington 70mm diameter x 17mm Scales: D ( C ) ( B ) A(inverted) / W Note: Unusual inner scale with W scale (-30 to +60) inserted into inverted logarithmic A scale. Scan donated by Paul Tarantolo, Houston, Texas
Lord's Calculator - (Elliot Brothers)	Lord's Calculator - (Elliot Brothers) Made in LOndon, England by Elliot Brothers 65mm diameter x 12.5mm Scales: D ( C ) ( B ) A(inverted) Scan donated by Paul Tarantolo, Houston, Texas

Molter, Wilhelm

Molter Slide Rule - "Mid" Model	Molter Slide Rule - "Mid" Model Made in Nuremburg, Germany by Wilhelm Molter 65mm diameter x 5.5mm Front scales: A, C ( D ) Back scales: n1, n3, tg, sin, log Opaque cursor grips Scan donated by Paul Tarantolo, Houston, Texas
Molter Slide Rule - Late Model	Molter Slide Rule - Late Model Made in Nuremburg, Germany by Wilhelm Molter 65mm diameter x 5.5mm Front scales: A, C ( D ) Back scales: n1, n3, tg, sin, log Transparent cursor grips Scan donated by Paul Tarantolo, Houston, Texas

G. Small (Boston)

G. Small - Pocket Calculator

G. Small - Pocket Calculator, c.1918
Made in U.S.A. by G. Small of Boston
Patent February 12, 1918
49mm diameter x 11mm
Front scales: 6", C, S
Edge scales: C || D
Back scales: L, A(2 turns), ST
Note: The edge scales slide past one another when the two halves are rotated.
Scan donated by Paul Tarantolo, Houston, Texas

Soviet KL-1

C10 Soviet KL-1 Slide Rule watch	Soviet KL-1 Slide Rule watch Made in USSR 5cm diameter Front Scale Instruction Sheet (Russian) 1.9Mb Instruction Sheet (English) 138Kb
REF - Soviet KL-1 Slide Rule watch	Soviet KL-1 Slide Rule watch Made in USSR 5cm diameter Front Scale Archive - Not in collection Insert (Russian) 990Kb Instruction Sheet (English) 138Kb

Sperry's Pocket Calculator

K&E 4017 Sperry's Pocket Calculator	K&E 4017 Sperry's Pocket Calculator - c1908-1911 Made in USA, Mfg by K&E - Designed by Elmer A. Sperry, US Pat# 773,235 Oct 25, 1904 Dual Revolving Scales: S Dial: Tan, Log (equal parts), Sin (2 spirals) L Dial: C (3 spirals) Archive - Ebay picture, Courtesy of Clark McCoy
K&E 4017 Sperry's Pocket Calculator	K&E 4017 Sperry's Pocket Calculator - c1903 Made in USA, Mfg by K&E - Designed by Elmer A. Sperry, US Pat.#773,235 Dual Revolving Scales: S Dial: Tan, Log (equal parts), Sin (2 spirals) L Dial: C (3 spirals) Archive - Ebay picture, Courtesy of Clark McCoy
K&E 4017 Sperry's Pocket Calculator	K&E 4017 Pocket Calculator sn S978 Made in USA, Mfg by K&E, - Designed by Elmer A. Sperry, US Pat.#773,235 Dual Revolving Scales: S Dial: Tan, Log (equal parts), Sin (2 spirals) L Dial: C (3 spirals) Archive - Ebay picture, Courtesy of Clark McCoy

Stanley-Boucher

Boucher's Calculator (Circular Mannhiem)	Boucher's Calculator Made in London, England by W.F. Stanley 52mm diameter x 14.5mm Front scales: S , C Square Root(2 Turns) Back scales: L, Cube Root(3 Turns) Scan donated by Paul Tarantolo, Houston, Texas
Stanley-Boucher's Calculator	Stanley-Boucher's Calculator Made in London, England by W.F. Stanley 52mm diameter x 16mm Front scales: S, C, Square Root(2 Turns) Back scales: L, Cube Root(3 Turns) Decimal Point Counter Scan donated by Paul Tarantolo, Houston, Texas

Mechanical Engineer Chronograph - 3 sizes	Mechanical Engineer Chronograph c1900-1910 Made in Manchester, England by Thomas Fowler Fowler was also known as: Scientific Publishing Company Archive - Jim Bready Collection (UK)
Fowler's Junior Calculator	Fowler's Junior Calculator Made in Manchester, England by Thomas Fowler 9 cm diameter Front Scales: C, CI, L, cube root (3 circle), S (2 circle), T Back Scales: C (D, L, square roots (2 circles), S, T) Archive - Courtesy of Rod Lovette's Collection (UK)
Fowler's Twelve-Ten Calculator	Fowler's Twelve-Ten Calculator Made in Manchester, England by Thomas Fowler 8.6 cm diameter Front Scales: C, CI, D, D, S, ST, T Note: Two "D" scales. On sub-divided in tenths and the other twelfths. Archive - Courtesy of Rod Lovette's Collection (UK)
Fowler's Calculator	Fowler's Calculator Made in Manchester, England by Thomas Fowler 68 mm diameter Front Scales: D, C, B, A Back Scales: L, C, A, S Archive - Herman van Herwijnen's Slide Rule Catalogue
Fowler's Calculator - Type H	Fowler's Calculator - Type H Made in Manchester, England by Thomas Fowler 68 mm diameter x 13mm Front Scales: C(short scale), CI, L, A(2 turns), S Back Scales: C(short scale Cubes), K (3 turns Cube roots) Scan donated by Paul Tarantolo, Houston, Texas
Fowler's Calculator - Type RX	Fowler's Calculator - Type RX Made in Manchester, England by Thomas Fowler 68 mm diameter x 13mm Front Scales: C(short scale), C(long scale - 6 turns) Back Scales: C(short scale), CI, L, A (2 turns), S Scan donated by Paul Tarantolo, Houston, Texas
Fowler's Universal Calculator	Fowler's Universal Calculator Made in Manchester, England by Thomas Fowler 86mm diameter x10 mm Front Scales: Conversion Yards to Metres C CI L 100-10 (in 3 circles), sin(6°-70°), sin(0°-5°) tan Archive - Courtesy of Rod Lovette's Collection (UK)
Fowler's Universal Calculator	Fowler's Universal Calculator Made in Manchester, England by Thomas Fowler 86mm diameter x10 mm Front Scales: Conversion Yards to Metres C CI L 100-10 (in 3 circles), sin(6°-70°), sin(0°-5°) tan Archive - Herman van Herwijnen's Slide Rule Catalogue
Fowler's Long Scale Calculator	Fowler's Long Scale Calculator - Established 1898 Made in Manchester, England by Thomas Fowler 68.5 mm Diameter x 11.5 mm Front Scales: L 3 revolution B scale Back Scales: C 6 revolution B scale Courtesy of Rod Lovette's Collection (UK)
Fowler's Long Scale Calculator	Fowler's Long Scale Calculator - Established 1898 Made in Manchester, England by Thomas Fowler 68.5 mm Diameter x 11.5 mm Front Scales: L 3 revolution B scale Back Scales: C 6 revolution B scale Archive - Herman van Herwijnen's Slide Rule Catalogue
Fowler's Long Scale Calculator	Fowler's Long Scale Calculator Made in Manchester, England by Thomas Fowler 68.5 mm diameter x 11mm Front Scales: C(short scale), C(longscale - 6 turns) Back Scales: None Scan donated by Paul Tarantolo, Houston, Texas
Fowler's Long Scale Calculator - 3 stems	Fowler's Long Scale Calculator - 3 stems Made in Manchester, England by Thomas Fowler 68 mm diameter x 11mm Front Scales: C(short scale), C(longscale - 6 turns) Back Scales: C(short scale), CI, L, A(2 turns), LogS, LogT, LogS Scan donated by Paul Tarantolo, Houston, Texas
Fowler's "Magnum" Long Scale Calculator	Fowler's "Magnum" Long Scale Calculator - 1927 Made in Manchester, England by Thomas Fowler 11.9 cm (4-5/8") Diameter x 1.1 cm Front Scales: C (short scale), CI, R1, R2, L, C (6 turn long scale 50"), S, S, T Back Scales: None Courtesy of Rod Lovette's Collection (UK)
Fowler's "Magnum" Long Scale Calculator Variation 1	Fowler's "Magnum" Long Scale Calculator Variation 1 Made in Manchester, England by Thomas Fowler 11.9 cm (4-5/8") Diameter x 1.1 cm Front Scales: C (short scale), CI, R1, R2, C (6 turn long scale 50"), L, S, S, T Back Scales: None Courtesy of Rod Lovette's Collection (UK)
Fowler's Jubilee magnum Extra Long Scale Calculator	Fowler's Jubilee magnum Extra Long Scale Calculator Made in Manchester, England by Thomas Fowler 119.5mm diameter x 11 mm Front Scales: 1, C, CI, L, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 Courtesy of Rod Lovette's Collection (UK)
Fowler's Jubilee magnum Extra Long Scale Calculator	Fowler's Jubilee magnum Extra Long Scale Calculator Made in Manchester, England by Thomas Fowler 119.5mm diameter x 11 mm Front Scales: 1, C, CI, L, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 Archive - Herman van Herwijnen's Slide Rule Catalogue
Fowler Artillery Calculator	Fowler Artillery Calculator Made in Manchester, England by Thomas Fowler Scan donated by Christopher Johnston, Omaruru Namibia
Fowler's Artillery Calculator	Fowler's Artillery Calculator Made in Manchester, England by Thomas Fowler 68 mm diameter x 11mm Front Scales: C(short scale), CI, LogSine, LogTan, Log Sine (small angle), Log Back Scales: Conversions: Yards/Miles, Miles/Km, Inches/mm, mm/inches Scan donated by Paul Tarantolo, Houston, Texas
Fowler's Textile Calculator - Type E1	Fowler's Textile Calculator - Type E1 Made in Manchester, England by Thomas Fowler 68 mm diameter x 10.5mm Front Scales: C(short scale), 8's Back Scales: Circular Table: Wefts, Looms, Reeds Scan donated by Paul Tarantolo, Houston, Texas
Fowler's Textile Calculator - Short Scale Type	Fowler's Textile Calculator - Short Scale Type Made in Manchester, England by Thomas Fowler 68 mm diameter x 10.5mm Front Scales: C(short scale), 8's Back Scales: Circular Table: Wefts, Looms, Reeds Scan donated by Paul Tarantolo, Houston, Texas
Fowler Textile Calculator	Fowler Textile Calculator - 2.5 inch diameter Made in Manchester, England by Fowler's Calculators Ltd Courtesy of Rod Lovette's Collection (UK)
Fowler's Textile Calculator - Type B (variant)	Fowler's Textile Calculator - Type B (variant) Made in Manchester, England by Thomas Fowler 87 mm diameter x 11mm Front Scales: C(short scale - 10ths and 16ths) Back Scales: None Scan donated by Paul Tarantolo, Houston, Texas
Fowler's Textile Calculator - Type B (variant)	Fowler's Textile Calculator - Type B (variant) Made in Manchester, England by Thomas Fowler 87 mm diameter x 11mm Front Scales: C(short scale - 10ths and 16ths) ± Scale (-40 to +60) Back Scales: None Scan donated by Paul Tarantolo, Houston, Texas
Fowler "Magnum" Textile Calculator	Fowler "Magnum" Textile Calculator Made in Manchester, England by Fowler's Calculators Ltd Scan donated by Monroe Postman, Los Altos, California