Graphoplex is a French manufacturer of slide rules that also supplied slide rules for Koh-I-Noor, a European company, still in business, with subsidiaries in the USA.

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Graphoplex - Caltex Petroleum (Model 615 with Viscosity Nomogram) c1968 ISRM 15.10.13.01 Caltex began in 1936 as the California Texas Oil Company, a joint venture between the Texas Company (later named Texaco) and Standard Oil of California (later named Chevron Corp.) to market oil from newly gained concessions in Saudi Arabia. It was renamed Caltex Petroleum Corp. in 1968. The two parent companies merged in 2001 to form ChevronTexaco (renamed Chevron in 2005) and Caltex remains one of its major international brand names.	Graphoplex - Caltex Petroleum (Model 615 with Viscosity Nomogram) Made in France for Caltrex, a division of Texaco Oil Company Front Scale (Conventional Labels): 17cm // B³(K), B²(A) [ b²(B), a(CI), b(C) ] B(D), L Reversible Slide: [ °A.P.I. (Gravity), D ] Back scale (Nomogram): Degrees Engler(at 0°C), Saybolt Univ (at 100°F), Degrees Engler (at 50°C), Centistokes, Saybolt Univ.(at 210°F), Degrees Engler(at 100°C) Well: Farenheight to Celsius conversion. Note 1: The American Petroleum Institute gravity, or API gravity, is a measure of how heavy or light a petroleum liquid is compared to water: if its API gravity is greater than 10, it is lighter and floats on water; if less than 10, it is heavier and sinks. Note2: the cursor is removable to place on the back side to calculate the viscosities on the nomogram. Gifted by Kenneth Eyre of the United KIngdom. Graphoplex System Rietz Instructions (French)- 842KBb
Graphoplex - CALCRUDE Oil Viscosity Slide Rule ISRM 22.03.01.74	Graphoplex - CALCRUDE Oil Viscosity Slide Rule (Model 615 with Viscosity Nomogram) Made in France for Calcrude, a division of Chevron Oil Company Front Scale (Extended Scales) 17cm // B³(K), B²(A) [ b²(B), a(CI), b(C) ] B(D), L Back: Nomograph for determining viscosity of oil at varying temperatures. Cursor: unusual lens with diagonal hairline to use on back side nomograph. Well: Farenheight to Celsius conversion. Note 1: The American Petroleum Institute gravity, or API gravity, is a measure of how heavy or light a petroleum liquid is compared to water: if its API gravity is greater than 10, it is lighter and floats on water; if less than 10, it is heavier and sinks. Note2: the cursor is removable to place on the back side to calculate the viscosities on the nomogram. Gifted by Philip Stanley of Worcester, MA
Graphoplex - CEFEM - Methane Gas Combustion REF P195	Graphoplex - CEFEM - Methane Gas Combustion Conditions D'Empli De La Règle De Combustion Du Gaz De Lacq Made in France for Compagnie Francaise Du Methane (CEFEM) Front Scale L, A, B³, B² [ b², a, b ] B, LL3, LL2, LL1 Back scale e%, O₂ %, CO₂ % [ CO%(e), CO%, CO₂% ] t°C, t°F, ρ/PCI, ρ/PCS Instructions - 2.84Mb
Graphoplex 610 Rietz REF S298	Graphoplex 610 Rietz Made in France Front Scale (Extended Scales) K, A [ B, CI, C ] D, L Back: Blank
Graphoplex 612 REF P167	Graphoplex 612 Made in France Front Scale (Extended Scales) 13cm // K, A [ B, CI, C ] D, L Back scale: [S, ST, T] Back Name: Papeterie Joseph Gibert
Graphoplex 614 Simplex Log Log REF S461	Graphoplex 614 Simplex Log Log Made in France - 1964 - Dual labeled: Left-French, Right-(Conventional) Front Scale (Extended Scales) 13cm // LL2, LL3, B³(K), B²(A) [ b²(B), L, a(CI), b(C) ] B(D), S cos, S&T, T ctg Back scale: Blank
Graphoplex 615 System Rietz REF P228	Graphoplex 615 System Rietz Made in France - C1964 Front Scale (Extended Scales) 17cm // K, A [ B, CI, C ] D, L Back scale: [S, ST, T] Multi-lined cursor
Graphoplex 620d System Rietz REF S462	Graphoplex 620d System Rietz Made in France - 1962 - French labels Front Scale (Extended Scales) 27cm // B³(K), B²(A) [ b²(B), L, a(CI), b(C) ] B(D), L Back scale: [ S Cos, S&T, T ctg ] Multi-lined cursor
Graphoplex ref. 620 System Rietz REF S464	Graphoplex ref. 620 System Rietz Made in France - 1964 - Conventional Labels Front Scale (Extended Scales) 27cm // K, A [ B, CI, C ] D, L Back scale: [SRT, S Cos, T<45°, C] Multi-lined cursor
Graphoplex 640 System Electric Log Log REF S460	Graphoplex 640 System Electric Log Log Made in France - Dual labeled: Left-French, Right-(Conventional) Front Scale (Extended Scales) 27cm // L, B³(K), B²(A) [ b²(B), K, a(CI), b(C) ] B(D), LL3, LL2, LL1 Back scale: [ cos, sin, tg, b(C) ] Back: Electrical Equations and Diagrams Multi-lined cursor
Graphoplex 640 System Electric Log Log ISRM 22.10.14.02	Graphoplex 640 System Electric Log Log Made in France - 1958 Front Scale (Extended Scales) 27cm // L, P, A [ B, K, CI, C ] D, LL3, LL2, LL1 Back scale: [ ST, S Cos, T<45°, C] Multi-lined cursor Donated by John Holmes of Washington, D.C.
Graphoplex 640 System Electric Log Log ISRM 09.01.12.137	Graphoplex 640 System Electric Log Log Made in France - 1958 Front Scale (Extended Scales) 27cm // L, P, A [ B, K, CI, C ] D, LL3, LL2, LL1 Back scale: [ ST, S Cos, T<45°, C] Multi-lined cursor Donated by David Hecht, Alexandria, VA
P227 Graphoplex 643 Electric Log Log	Graphoplex 643 Electric Log Log Made in France - 1964 - Dual labeled: Left-French, Right-(Conventional) Front Scale (Extended Scales) 27cm // L, cos, B³(K), B²(A) [ b²(B), a(CI), b(C) ] B(D), LL3, LL2, LL1 Back scale: [ S&T, S, T, b(C) ] Back: Blank Multi-lined cursor
S459 Graphoplex 645 System Commercial	Graphoplex 645 System Commercial Made in France - 1958 Front Scale (Extended Scales) 27cm // DF [ CF, CI, C ] D, £, s/d, Conversions Back scale: [ LL3, LL2, LL1, C] Back: Examples of Interest Calculations
REF Graphoplex 650 Electro	Graphoplex 650 Electro Made in France Typical of the French, they just had to change the scale tags. Normal in () Front Scale (Extended Scales) 13cm // L, B³(K), COSφ, B²(A)Kw [ b²(B)PS, a(CI), b(C) ] B(D), COSφ, Dynamo/Moteur, Volt Back scale: [S&T, S, T, b(C) ] Archive - Atsushi Tomozawa Collection
Graphoplex 690A Neperlog Duplex ISRM 05.02.15.01	Graphoplex 690A Neperlog Duplex Made in France - 1964 Front Scale (Extended Scales) LL01, LL02, LL03, DF [ CF, CIF, K, CI C ] D, LL3, LL2, LL1 Back Scale: LL00, L, T&rt;45°, A [ B, T<45° Cot, SRT, S Cos, C, D, P, DI, LL0 Multi-lined cursor
Graphoplex 691 Neperlog - Hyperbolic Duplex REF	Graphoplex 691 Neperlog - Hyperbolic Duplex Made in France - 1964 Original Model Front Scale L, P, A [ B, T<45°, SRT, S, C ] D, Th, Sh1, Sh2 Back Scale: LL01, LL02, LL03, DF [ CF, CIF, K, CI, C ] D, LL3, LL2, LL1 Multi-lined cursor Archive photo
Graphoplex 691A Neperlog - Hyperbolic Duplex REF	Graphoplex 691A Neperlog - Hyperbolic Duplex Made in France - 1964 Front Scale (extended) L, P, A [ B, T<45°, SRT, S, C ] D, Th, Sh1, Sh2 Back Scale: LL01, LL02, LL03, DF [ CF, CIF, K, CI, C ] D, LL3, LL2, LL1 Multi-lined cursor Archive - Scan courtesy of Rod Lovette collection
Graphoplex 692 REF	Graphoplex 692 Duplex Made in France Front Scale L, P, AI, A, [ B, T (t), S&T, S Cos ] D, DI, K Back Scale: LL01, LL02, LL03, DF [ CF, CIF, CI, C ] D, LL3, LL2, LL1 Archive - Not in Collection - D'Antiques
Graphoplex 692b Neperlog REF	Graphoplex 692b Neperlog - Duplex Made in France Front Scale (Extended scales) LL00, L, T>45°, A [ B, T<45°, SRT, S C ] D, P, DI, LL0 Back Scale: LL01, LL02, LL03, DF [ CF, CIF, K, CI, C ] D, LL3, LL2, LL1 Archive - Not in Collection - SRTG
Graphoplex 1600 System Rietz ISRM 09.01.12.129	Graphoplex 1600 System Rietz Made in France Front Scale (Extended Scales) 27cm // L, T>45° Cot, A [ B, K, CI, C ] D, S Cos, ST, T<45° Cot Back: Blank Donated by David Hecht, Alexandria, VA
Graphoplex 1600 System Rietz ISRM 18.04.06.128	Graphoplex 1600 System Rietz Made in France. Note Blue Tint Scales Front Scale (Extended Scales) 27cm // L, T>45° Cot, A [ B, K, CI, C ] D, S Cos, ST, T<45° Cot Back: Blank Gift of Leroy Hausler Collection
Graphoplex 1614 System Log Log REF S465	Graphoplex 1614 System Log Log Made in France - 1958 Front Scale (Extended Scales) 27cm // LL2, LL3, L, A [ B, K, CI, C ] D, S Cos, ST, T<45° Cot Back: Blank Multi-lined cursor
Graphoplex 1694 Techni-Math REF	Graphoplex 1694 Techni-Math Made in France - 1961 Front Scale (Extended Scales) 27cm // P, K, A, DF [ CF, L, CI, C ] D, S Cos, SRT, T, Cot Back: Blank Multi-lined cursor Archive - Image from Herman van Herwijnen's Catalogue
Graphoplex_Insert REF	Graphoplex_Insert Provided with most slide rules Calculation aids and instructions for care of slide rule (French)

Koh-i-Noor Hardtmuth a.s. is a Czech manufacturer and one of the world's largest producers and distributors of a full line of pencils, pens, and art supplies.[1] Formed in 1790 by Joseph Hardtmuth of Austria, the company was named after the Koh-i-Noor, a famous Indian diamond. In 1802, they patented the first pencil lead made from a combination of clay and graphite. Koh-i-Noor Hardtmuth eventually became a state-owned company after the Second World War, before once again becoming privately held in 1992 and being bought-out in 1994 by the Gama Group. Prior to 1978 they were a reseller of slide rules made by Graphoplex are also a contract manufacturer of small injection-molded plastic products.

In the United States the Graphoplex slide rules were rebranded and distributed by Koh-I-Noor Inc, Bloomsbury, New Jersey 08804. The USA branch was founded in 1890.

Koh-I-Noor Slide Rules Fabrik Pvt. Ltd in India, (the relationship with Koh-I-Noor Hardtmuth is unknown), is still making special purpose plastic slide rules, including circular computers for aviation.They say on their web site: "We are the pioneer manufacturers of Slide Rules in India! In the year 1949, our company started the production of Slide Rules in 6" & 12" sizes for students, professionals and Army."


Koh-I-Noor 10000 Koh-I-Log Log Log Duplex ISRM 22.07.06.13 Replaced 14.01.10.20	Koh-I-Noor 10000 Koh-I-Log Log Log Duplex Made in France by Graphoplex - c1961 Note: Same as Graphoplex 690A Neperlog, except the cursor only has one hairline on both sides. Front Scale (Extended Scales): LL01, LL02, LL03, DF [ CF, CIF, K, CI C ] D, LL3, LL2, LL1 Back Scale: LL00, L, T&rt;45°, A [ B, T<45° Cot, SRT, S Cos, C, D, P, DI, LL0 Gift Of Cindy Tate of Bozeman, Montana
Koh-I-Noor 10010 Techno-Log Log Log Duplex ISRM 21.05.24.01	Koh-I-Noor 10010 Techno-Log Log Log Duplex (c1961) Made in France by Graphoplex. Distributed by Koh-I-Noor Inc, Bloomsbury, New Jersey 08804. Front Scale (Extended Scales): LL02, LL03, DF [ CF, CIF, K, CI C ] D, LL3, LL2 Back Scale: LL01, L, A [ B,T Cot, SRT, S Cos, C ] D, DI, LL1
Koh-I-Noor 10020 Techni-Math ISRM 09.01.12.131	Koh-I-Noor 10020 Techni-Math Made in France - c1961 Front Scale (Extended Scales) 10 in // P, K, A, DF [ CF, L, CI, C ] D, S Cos, SRT, T, Cot Back: Blank Multi-lined cursor Donated by David Hecht, Alexandria, VA