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Pocket Watch Style Logarithmic Circular Slide Rule Calculators


KEEP ISRM FREE!
This page contains circular slide rules in the form of a pocket watch. They are not time pieces. 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.

Wrist Watch Time Pieces/Chronographs
with Logarithmic Scales for Calculations


Visit this forum on Breitling The Slide Rule Chronomats
.


Swiss makers, and brands made by the Swiss, were Arios, Breitling, Camy, Certina, Chase Durer, Cimier, Clebar, CX Swiss Military, ESQ, Fortis, Fero, Formex, Gallet, Girard-Perregaux, Hacher, Hamilton, Heuer, Ikepod, Juvenia, LeCoultre, Luminox, MIMO, Mondia, Ollech & Wajs, Orator, Revue Thommen, Sector, Selectron, Sheffield, Sinn, Sicura, Sorna, Tissot, Torgoen, Tourneau, Ventura, Wenger, Wittnauer, Zeno. French makers were: Meyrat & Perdrizet, Eberjax and Yema. Post WWII japanese manufacturers were: Seiko, Citizen, Casio, Orient and Kentex. Other known manufacturers are/were: Abingdon, Accurist, Aeromatic, Alpha, Anonimo, Bulova, Ellesse, Estana, Honda, Invicta, Jeep, Jules Jurgensen, Kenneth Cole, Kienzle, National Geographic, Nautica, Sea Gull, Sekonda, Timex, Tommy Bahama, Trias, Poljot, Rendex, Rotary, and Vostok. Many are now replicas out of China.

The modern slide rule/chronograph wristwatch has a relatively recent origin, arriving in 1940 during the beginnings of World War 2 by the Swiss, although the first known example of a time piece with a calculator was by the French Meyrat & Perdrizet around 1890. This was in the form of a pocket watch as seen here.


French Meyrat & Perdrizet (1890)

The beginning of WWII brought an influx of orders to the Swiss watch manufacturers from all over the world, and with it came the introduction of new watch models with new features. A slide rule wristwatch has two (or more) logarithmic scales. Usually, one scale is on a movable bezel, and a second is fixed or printed on the face of the watch. Calcuations are made by rotating the bezel to fix the relative position the two scales. The two scales form proportions that are useful in math problems involving multiplcation and division. The first three modern manufacturers, all Swiss, were Breitling, Juvenia and MIMO.

Charpentier



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

Fowler & Co. Manchester, England.


1905 Photo and 1926 Parts Diagram
Established in 1898 on Hampson Street, Manchester, England by William Henry Fowler (1853 - 1932). Fowler made over fifty variations of circular 'pocket watch' calculators with logarithmic slide rule scales. They continued manufacturing up to 1988. See Fowler history Timeline
See Fowler's Long Scale Calculator Instructions by Ron Manley, UK.


Fowler's Junior Calculator
REF
Fowler's Junior Calculator
Made in Manchester, England by William H. 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
REF
Fowler's Twelve-Ten Calculator
Made in Manchester, England by William H. 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
REF
Fowler's Calculator
Made in Manchester, England by William H. 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
REF
Fowler's Calculator - Type H
Made in Manchester, England by William H. 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
REF
Fowler's Calculator - Type RX
Made in Manchester, England by William H. 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

ISRM 18.08.06.01


John Napier and Sir Joseph Whitworth images from the manual
Fowler's Universal Calculator
Made in Manchester, England by William H. Fowler
86mm diameter x10 mm
Front Scales: Conversion Yards to Metres, C CI Logs 100-10 (in 3 circles), sin(6°-70°), sin(0°-5°), tan
Belonged to Richard Levy (1932-2017)
Gifted by wife Midge Levy and son Benjamin Levy, Seattle, Washinbgton.

Richard Levy

Sleeve
Richard Levy 1932 - 2017 was born in London, and as a child, he was evacuated to Montreal to escape the Blitz during the WWII, He returned to London in 1943 to complete his schooling and graduated from Cambridge with a BA in Math. He married Midge in 1955, and then moved to the USA. He received a Fellowship at Princeton University and earned a PhD in Aeronautical Engineering. During this time he made extensive use of his slide rules. He returned to Montreal to begin his career at Canadair, and subsequently moved to Boston where he worked for AVCO during the 1960s and 1970s. At AVCO he began work on laser applications, and coauthored a number of patents regarding their use in the separation of isotopes which has important applications in the production of nuclear energy. This accomplishment led to the formation of a joint venture between Avco and Exxon, and in 1974 he moved to Seattle to begin work with this new entity. He left corporate life in 1980, retiring in Seattle. He spent retirement consulting and studying issues such as the Allies decision not to bomb the rail lines leading to Auschwitz. He enjoyed the outdoors, the symphony and the opera, and was proud of his heritage.


Fowler's Universal Calculator
REF
Fowler's Universal Calculator
Made in Manchester, England by William H. 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
REF
Fowler's Long Scale Calculator - Established 1898
Made in Manchester, England by William H. 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
REF
Fowler's Long Scale Calculator - Established 1898
Made in Manchester, England by William H. 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
REF
Fowler's Long Scale Calculator
Made in Manchester, England by William H. 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
REF
Fowler's Long Scale Calculator - 3 stems
Made in Manchester, England by William H. 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 (1927)

ISRM 18.10.01.01
Fowler's "Magnum" Long Scale Calculator - 1927
Made in Manchester, England by William H. 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


Fowler's "Magnum" Long Scale Calculator Variation 1
REF
Fowler's "Magnum" Long Scale Calculator Variation 1
Note: The word "Magnum" is more pronounced and below the pivot
Made in Manchester, England by William H. 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

ISRM 15.03.06.01
Fowler's Jubilee Magnum Extra Long Scale Calculator
Made in Manchester, England by William H. Fowler 
119.5mm diameter x 11 mm
Front Scales: Metric Conversions, C, CI, L, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11
Note: Acquired from the United KIngdom


Fowler Artillery Calculator
Fowler Artillery Calculator
Made in Manchester, England by William H. Fowler 
Scan donated by Christopher Johnston, Omaruru Namibia


Fowler's Artillery Calculator
Fowler's Artillery Calculator
Made in Manchester, England by William H. 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 William H. 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 (One Knob)
Fowler's Textile Calculator - Short Scale (One Knob)
Made in Manchester, England by William H. 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 - Short Scale (Two Knobs)

ISRM 15.09.27.08
Fowler Textile Calculator - Short Scale (Two Knobs)
Made in Manchester, England by William H. Fowler
68 mm diameter x 10.5mm
Front Scales: C(short scale), 8's
Back Scales: Circular Table: Wefts, Looms, Reeds


Fowler's Textile Calculator - Type B (variant)
Fowler's Textile Calculator - Type B (variant)
Made in Manchester, England by William H. 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 William H. 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

Halden, Joseph



Halden Calculex - Pocket Model

ISRM 15.07.20.01


Instructions (19.2MB) and Sleeve

R.W Kratz Sr. with Nick Kratz's father R.W. Kratz Jr.
Halden Calculex Patent Calculator - 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) ]
Gift of Nick Kratz of Pasadena, California. Belonged to his grandfather R.W. Kratz Sr.

Nick Kratz writes" This is [part of - See K&E gallery] the combined surviving collection of my father, R.W. Kratz Jr,( - 2008) and father, R.W. Kratz, Sr.( - 1942)
My grandfather (Sr.) who, amongst other things, was an electrical and HVAC engineer . My father was in International Licensing, and as i recall worked with a company in the UK (unfortunately i don't remember which company, and my father died in 2008) which licensed the Hughes-developed IC and did bring a product to market (4-function, not scientific, so not directly threatening slide rules. This would have been 1972 or thereabouts). I was 16 years old in 1975. I remember my father showing me, maybe a few years prior, how to use a slide rule. This was of course happening as the affordable scientific calculators were rolling out, bringing with them disruptive change. I never did have enough interest to learn the slide rule, with simple battery-operated greater precision at my fingertips. My loss if i survive the end of the world where there is a slide rule but no functioning calculator, though given that I'm having trouble surviving in this world as it is, I'm not particularly concerned about that. ;-) I was amongst the first engineering generation (electrical, in my case) who started out with calculators and never used slide rules."


Halden Calculex - Pocket Model (Early)

ISRM 15.09.27.07
Halden Calculex Patent Calculator - Pocket Model (early)
Note: This is an earlier version where the inner scales were blocked slightly by the knurled knobs.
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) ]


Halden Calculex - Pocket Model

REF
Halden Calculex Patent Calculator - Pocket Model
Made in Manchester, England by Joseph Halden
Note: This is a later version where the inner scales were made with a slightly larger diameter, and the knurled knobs smaller, so the scales would not blocked by the knurled knobs.
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

REF
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

F. C. Calculigraphe



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

REF
F.C. Calculigraphe (Calculating Circle) Boucher's System
Made in Paris, France (possibly by Henri Chatelain's brother Fred, 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 Clay Castleberry, California

Henri Chatelain Calculigraphe



H. C. Calculigraphe (Calculating Circle) Boucher's System/a>
ISRM 15.09.27.11
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


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

ISRM 15.09.27.11
H.C. Calculigraphe (Calculating Circle) Boucher's System
Made in Paris, France by Henri Chatelain, c.1878
Note logo graphic below H.C.
52.5mm diameter x 17.5mm
Front scales: L, Cube Root(3 Turns)
Back scales: S, C, Square Root(2 Turns)

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)

REF
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)

REF
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

REF
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

REF
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

Gilbert Small, Waltham, Massachusetts


Photos of Gilbert and Christine Small

Gilbert Small (1885-1963) invented and manufactured The Small Calculator in 1917. Jonathan Small, his Grandson, writes: "The only tidbit I know about the Pocket Calculator is that my grandmother mentions in her diaries from the 1920s a number of occasions when she and my grandfather would spend an evening assembling calculators to fill orders. Gilbert Small was employed by an engineering firm by the name of Worcester with offices in Waltham and Boston." (Continued on right)

(Cont'd) "He was frequently required to make trips to Portland, ME, to inspect a bridge there (a bridge known as the 'Million Dollar Bridge', which has since been torn down). As a small child I knew my grandfather had invented the 'Small Pocket Calculator' because he had quite a few in stock in his home in Wayland, Massachusetts. His work was in the field of architecture for which he regularly commuted from Wayland (a suburb) to Boston by train. He was instrumental in designing the colonial style home (also in Wayland) where my parents brought up their family and lived well into their senior years, Sometimes my grandfather's work involved dismantling old historical New England homes. When this was the case he frequently salvaged and recycled useful building materials. In the case of my childhood home, this included massive exposed hand hewn beams in the living room. You could see the marks where someone had shaped the beams one axe blow after another. He also recuperated broad planks of red pine paneling and vintage bricks for that house. His architectural work prompted him to invent the 'Small Pocket Calculator'. He designed it in an era before wristwatches had come into vogue and it was common for men to carry a pocket watch. My grandfather wanted to make a calculator that would have the same small, round and convenient size and shape."



The Small Calculator (1917)

ISRM 14.06.12.01

The Small Calculator
Made in USA by Gilbert Small, Waltham, Massachusetts
United Staes Patents 657,916 Sep 18, 1900 and 1,255,939, Feb 12, 1918
Radial Scale: ( C, D )
Circular Scale Face 1: 6in Linear scale, CI, S
Circular Scale Face 2: L, A (2 concentric scales), ST
Gift Of Gretchen S. Lebrun (Canada) and Jonathan Small, Grand Children Of Gilbert Small
Related US patents: (Additional Photos courtesy of Nathan Zeldes\, Israel)
US0657916 US1255939
Scale Description

Soviet KL-1




Soviet KL-1 Slide Rule watch

C10
Soviet KL-1 Slide Rule watch
Made in USSR 5cm diameter
Front Scale
Instruction Sheet (Russian) 1.9Mb
Instruction Sheet (English) 138Kb



Soviet KL-1 Slide Rule watch

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


Soviet KL-1 Slide Rule watch, 50th Anniversary 1917-1967

REF
Soviet KL-1 Slide Rule watch, 50th Anniversary 1917-1967
Made in USSR 5cm diameter
Front Scale
Archive - Scan by Clay Castleberry, California

Meyrat & Perdeizet



Meyrat & Perdeizet Cercle A Calcul Slide Rule watch

REF
Meyrat & Perdeizet Cercle A Calcul Slide Rule watch
Made in France - 6 cm diameter, Circa 1880, French patent #139898
Front Scale: C ( D )
Archive - Scan by Clay Castleberry, California
Inner Works


E.A. Sperry's Calculator


Elmer Ambrose Sperry, Sr. (1860 - 1930) was an American inventor and entrepreneur, and slide rule collectors know him for inventing the Sperry's Calculator, a pocket watch slide rule that was made and distributed by K&E starting in 1903. He was most famous as co-inventor, with Herman Anschütz-Kaempfe of the gyrocompass and as founder of the Sperry Gyroscope Company. His compasses and stabilizers were adopted by the United States Navy and used in both world wars. He also worked closely with Japanese companies and the Japanese government and was honored after his death with a biography in his honor. More than fifty years of Mr. Sperry's life had been devoted to invention. At his death, he was said to have taken out nearly 400 patents, about double the number taken out by Edison.More at Wikipedia


E.A. Sperry's Calculator

ISRM 15.09.27.10
E.A. Sperry's Calculator - c1903
Made in USA, Mfg by K&E as No4017 - 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)
Note: No fob loop on edge . Edge has #375 on it

US Pat# 773,235 Oct 25, 1904, K&E Catalog Page


K&E 4017 Sperry's Pocket Calculator

REF
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

REF
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

REF
K&E 4017 Pocket Calculator sn S378
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

Scientific Publishing. Manchester, England.



Scientific Publishing Chronograph

ISRM 15.09.27.09
Scientific Publishing Chronograph c1900-1910
Made in Switzerland, Distributed out of Manchester, England by William H. Fowler
Fowler was also known as: Scientific Publishing Company




Mechanical Engineer Chronograph - 3 sizes

REF
Mechanical Engineer Chronograph c1900-1910
Made in Manchester, England by William H. Fowler
Fowler was also known as: Scientific Publishing Company
Archive - Jim Bready Collection (UK)


Mechanical Engineer Chronograph

REF
Mechanical Engineer Chronograph c1900-1910
Made in Switzerland, Distributed out of Manchester, England by William H. Fowler
Fowler was also known as: Scientific Publishing Company
Archive - Scan by Clay Castleberry Collection (California)


Stanley-Boucher



Boucher's Calculator (Circular Mannhiem)

REF
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

REF
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

Wichmann, Gebr., Berlin, Germany



Gebr. Wichman Pocket Watch Slide Rule (1938)

ISRM 15.09.27.07
Gebr. Wichman Pocket Watch Slide Rule (1938)
Made in Berlin, Germany.
70mm diameter x 10mm
Front scales: ?, A ( B ?, ? )
Back scales: sin, F (G1, G2, G3, G4)
Note: This specimen has a cellulois lens that have faded and warped. There bwas excessive abrasion on on side from the lens that wiped of the scales. Its hard to see the scales so another scan was performed with the Lens Removed. It was then noticed that the stem which spins the center dials was missing..

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