Updated Regularly Click REFRESH on your browser if pages seem unchanged Visit our amazing document server. Everything from SciFi to Ethics. Welcome To The Sphere Research Slide Rule Universe ! K+E, Slide Rules from one of America's premier manufacturers!  Sphere Research Corporation 3394 Sunnyside Rd. West Kelowna, BC, Canada V1Z 2V4 Phone: +1 (250) 7691834 FAX:+1 (250) 7694106 A great source for test equipment, repairs, calibrations, useful metrology information, and of course, SLIDE RULES! Just SCROLL DOWN to see everything! 
K+E's 38th catalog frontpiece, CLICK for larger pic! 
Mr. Wilhelm (William) Keuffel (left) and Mr. Hermann Esser (right), CLICK for larger pic! Archival photograph from recently discovered documents passed from K+E to Azon to Itellicoat at the dissolution of each company. From the 100th anniversary company memorial publication materials. Visit Clark McCoy's K+E Catalog Site. 
Thanks to Ray Brohinsky, here's the 100 year book files compressed and turned into a smaller (13mb) PDF document:

Page 36, showing K+E's corporate timeline versus major world events. CLICK for full size JPG file. 

The day the slide rules arrived... CLICK to see the full sized image! 
slide rule designs... CLICK to see the full sized image! 
Click to VISIT or RETURN Click Here To go to the Slide Rule Marketplace  An amazing tour with K+E from 1940. Learn How to Operate a Slide Rule with a 1928 K+E Lesson 
Keuffel & Esser Co. factories were based in Hoboken, New Jersey (USA), with offices in New York, Chicago, St. Louis, San Francisco, Detroit, and Montreal. Started in 1867, slide rules were only a very small part of K+E's product offering, which included everything from drafting paper to survey instruments and drafting aids. K+E held patents for a wide range of slide rule features, including improved cursor indicators, functions and scales, and the adjustable body mechanism. Caught by the huge market shift created by electronic calculators, CAD systems and laser surveying systems, which displaced all of their strong markets, K+E shrank dramatically after 1972. Slide rules were never very profitable for K+E, and production and most inventory was gone by the mid70's. K+E even sold some TI manufactured calculators for a brief period trying to capitalize on their existing customer base and industry knowledge. The final assets of K+E, mainly involving paper products, were sold to AZON in 1987, after several painful internal reorganizations. AZON also acquired the remaining assets of HughesOwens in 1988, and the POST Company in 1994, relating to it's principal business, which is drafting and reproduction paper and film. Only these paper products survived the shakeout in all these related businesses. Dietzgen still exists today, but like AZON, is mainly in the paper business, and itself was taken over by Intellicoat. Most K+E slide rules were originally implemented in mahogany, with celluloid white scale overlays, engraved scales and glass cursors. People (especially on eBay) often mistakenly think the scales on older K+E rules are made of Ivory, but they are not, they are made of white celluloid. Later slide rules like the 4097 were made from Xylonite, and then (4181, Decilon and Doric series) from "Ivorite", a smooth, white, long wearing plastic (Cycolac/ABS). Xylonite was quite brittle, and not an ideal body material, Ivorite was much better, more rugged, whiter in color, and has very good sliding/lubricating properties. K+E rule scales were normally engraved (sorry, "engine divided") for long wearing life, and often filled in different colors to accent inverse scales. A few inexpensive rules like the plain wood body 4058, have an impressed/printed scale. Glass magnifying cursor indicators were available, and increased the settability and resolution of virtually any rule, often making a 10" rule the effective equivalent of a 20" version. Reference data for the K+E magnifiers is shown towards the end of the table. Notes: It is somewhat unclear what the difference is between K+E slide rule numbers that have an "N" at the front, and those that do not. Catalogs do not clarify this, but according to Ed Chamberlain, it reflects subtle design differences in a scale or mechanical construction detail, with the N designation being the NEW version of the rule. This is only a partial clue, as many K+E rules, such as the venerable 4053 Mannheim rule, existed in many subtle variations of body, cursor and scale designs, but were not differentiated by any part number change (a highly confusing situation). This rule and many others were then finally renamed with a 68series number confusing matters even worse for collectors. Note that PIckett (a competitor) also added N to the front of rule numbers to indcate new physical designs. 40813 Log Log Duplex DeciTrig 681100 DeciLon 40533 Polyphase 40883 Duplex Polyphase "4000" series data here is from the 1936 K+E catalog and some later numbers from live examples, later "4100" series numbers and 68rules are taken from live examples and a 1964 K+E brochure. The dash number on these "4000" series rules indicates the size of the rule (based on the same scale pattern), and is the SCALE LENGTH, not the overall size of the rule itself. There was a brief period (50's) where K+E used a different numbering scheme beginning 90 (9081 for example) for DORIC brand Ivorite body rules but then changed back to 4100 series numbers. 68rules have no dash to indicate length, but had different ordering part numbers for different cases (with or without pocket clip or other case styles), although the slide rule number itself was not changed, raising confusion to new levels for all involved. Dating K+E slide rules is a complicated task, as serial numbers were recycled three times at K+E. Based on external clues from the body and cursor (although caution is needed there, as it may have been replaced), as well as case and manual details, and any copyright or patent dates, it is possible to place the rule within one of the three probable cycles. The copyright or patent date IS NOT the date of manufacture, and may be decades earlier than the real production date. Note that evidence from Decilon rules shows at least one additional cycle after the ones shown below, plus some random numbers after 1964. Considerable work was done to calculate these serial number cycles by Wayne Feely and Ed Chamberlain, and Ed's quick chart is provided here with permission to help you date your rules. Click on the chart to bring up a larger version! Note that Joe Soper identified many end of manufacture rules that had out of sequence parts, so rules made in the last year or so of production may have numbers that do not fit this chart. Click for bigger Chart!

K&E Model Number  Slide Rule Type  Size, Core Material  Scales Features  IMAGE LINKS (Back to Return) 
4012  Thatcher's Calculating Instrument  18" cylinder
Wood  20 angular segments No indicator, A, B, C Wood box  Click for Bigger Pic! 
4013  Thatcher's Calculating Instrument  18" cylinder
Wood  20 angular segments 3 inch reading glass, A, B, C Wood box  
4017  Sperry's Pocket Calculator  2 1/8" diameter, watch style
Metal, Glass  4 scales duplex indicator unknown  
4031S  Mannheim  5"
Wood  A, [ B, C, ] D, rulers, improved glass indicator, leather case  shows extra cursor 
N4035S  Mannheim  8"
Wood  A, [ B, C, ] D, rulers,
improved glass indicator, leather case  
N4041  Mannheim  10"
Wood  A, [ B, C, ] D, rulers,
improved glass indicator,  
N4041S  Mannheim  10"
Wood  A, [ B, C, ] D, rulers,
improved glass indicator, leather case  
4045  Mannheim  16"
Wood  A, [ B, C, ] D, rulers,
improved glass indicator,  
4045S  Mannheim  16"
Wood  A, [ B, C, ] D, rulers,
improved glass indicator, leather case  
4051  Mannheim  20"
Wood  A, [ B, C, ] D [ S, L. T ] on slide reverse, side rulers, improved glass indicator,  Partial with 4055 Below Rest of the 4051 Rule 
4051S  Mannheim  20"
Wood  A, [ B, C, ] D, rulers,
improved glass indicator, leather case  
40532S  Mannheim Polyphase  8"
Wood  inch A, [ B, CI, C, ] D, K, cm [ S, L, T ] improved glass indicator, leather case  
40533  Mannheim Polyphase  10"
Wood  inch A, [ B, CI, C, ] D K (edge) [ S, L, T ] frameless plate glass indicator,
Flap case  Click here for Bigger Pic Click here for Other Side Click here for Side Scale 
(N)40533  Mannheim Polyphase  10"
Wood  inch A, [ B, CI, C, ] D, K, cm [ S, L, T ] improved glass indicator,  
40533S  Mannheim Polyphase  10"
Wood  inch A, [ B, CI, C, ] D, K, cm [ S, L, T ] improved glass indicator, sewn leather case  
40533F  Mannheim Polyphase  10"
Wood  inch A, [ B, CI, C, ] D, K, cm [ S, L, T ] improved glass indicator, finer divisions  
40533FS  Mannheim Polyphase  10"
Wood  inch A, [ B, CI, C, ] D, K, cm [ S, L, T ] improved glass indicator, finer divisions, leather case  
(N)40535  Mannheim Polyphase  20"
Wood  inch A, [ B, CI, C, ] D, K, cm [ S, L, T ] improved glass indicator,  CLICK for BIGGER PIC CLICK for BIGGER PIC! CLICK for BACK CLICK for BIGGER PIC CLICK for BACK 
40535S  Mannheim Polyphase  20"
Wood  inch A, [ B, CI, C, ] D, K, cm [ S, L, T ] improved glass indicator, leather case  
4055  Mannheim Favorite  10"
Wood  A, [ B, C, ] D [ S, L, T ]  Click here for Bigger Pic Click here for Other Side 
4056  Mannheim Favorite  10"
Wood  A, [ B, C, ] D  
4058  Mannheim Beginner's  10"
Wood  A, [ B, C, ] D, plain wood, xylonite indicator  
4058C  Mannheim Beginner's  10"
Wood  A, [ B, C, ] D, plain wood, frameless (wood sided) indicator  Click here for Bigger Pic Click here for Other Side 
4058W  Mannheim Beginner's  10"
Wood  A, [ B, C, ] D, white finish, plain frame indicator 
40703  Polyphase Duplex Trig  10"
Wood  K, A, [ B, T, ST, S, ] D, DI &
DF, [ CF, CIF, CI, C, ] D, L Improved glass indicator. Trig scales degrees, minutes.  
40703S  Polyphase Duplex Trig  10"
Wood  K, A, [ B, T, ST, S, ] D, DI &
DF, [ CF, CIF, CI, C, ] D, L Improved glass indicator. Trig scales degrees, minutes. Sewed leather case.  Trig in minutes/seconds CLICK for BIGGER PIC 
40713  Polyphase Duplex DeciTrig  10"
Wood  K, A, [ B, T, ST, S, ] D, DI &
DF, [ CF, CIF, CI, C, ] D, L Improved glass indicator. Trig scales degrees, decimals.  
40713S  Polyphase Duplex DeciTrig  10"
Wood  K, A, [ B, T, ST, S, ] D, DI &
DF, [ CF, CIF, CI, C, ] D, L Improved glass indicator. Trig scales degrees, decimals. Sewed leather case  
40803  Log Log Duplex  10"
Wood  LL0, LL00, A, [ B, T, ST, S, ] D, DI, K &
L, LL1, DF, [ CF, CIF, CI, C, ] D, LL3, LL2 Improved glass indicator.
Trig scales inches, seconds, degrees.  TRIG in Minutes/Seconds! CLICK for bigger PIC CLICK for bigger PIC 
40805  Log Log Duplex  20"
Wood  LL0, LL00, A, [ B, T, ST, S, ] D, DI, K &
L, LL1, DF, [ CF, CIF, CI, C, ] D, LL3, LL2 Improved glass indicator. Trig scales inches, seconds, degrees.  
40813  Log Log Duplex Decitrig ©1947  10"
Wood  LL0, L, K, A, [ B, T, SRT (or ST), S, ] D, DI, LL1
LL02, LL03, DF, [ CF, CIF, CI, C, ] D, LL3, LL2 Improved glass indicator. Trig scales decimal degrees. Many cosmetic variations.  Click for other side! 
40813S  Log Log Duplex Decitrig ©1947  10"
Wood  LL0, L, K, A, [ B, T, SRT (or ST), S, ] D, DI, LL1
LL02, LL03, DF, [ CF, CIF, CI, C, ] D, LL3, LL2 Improved glass indicator.
Trig scales decimal degrees. Many cosmetic variations. 
CLICK for bigger PIC 
40815  Log Log Duplex Decitrig ©1947  20"
Wood  LL0, L, K, A, [ B, T, SRT, S, ] D, DI, LL1
LL02, LL03, DF, [ CF, CIF, CI, C, ] D, LL3, LL2 Improved glass indicator. Trig scales decimal degrees.  
40833  Hyperbolic Log Log Duplex  10"
Wood  Sh1, Sh2, Th, A, [ B, T, ST, S, ] D, DI, LL01, LL1
LL02, LL03, DF, [ CF, CIF, CI, C, ] D, LL3, LL2 Improved glass indicator. Hyperbolic Sine and Tangent Trig scales, used in the power industry.  HYPERBOLIC SCALES 
N40833S  Hyperbolic Log Log Duplex  10"
Wood  L, LL01, LL1, A, [ B, T, ST, S, ] D, Th, Sh1, Sh2,
LL02, LL03, DF, [ CF, CIF, CI, C, ] D, LL3, LL2 Improved glass indicator. Hyperbolic Sine and Tangent Trig scales (numerous scale layout variations), used in the power industry. Orange sewn leather case  HYPERBOLIC SCALES CLICK for bigger PIC CLICK for bigger PIC 
40881S  Polyphase Duplex  5"
Wood  K, A, [ B, S, T, CI, ] D, L &
DF, [ CF, CIF, C, ] D Frameless glass indicator, leather case  
40882S  Polyphase Duplex  8"
Wood  K, A, [ B, S, T, CI, ] D, L &
DF, [ CF, CIF, C, ] D Improved glass indicator, leather case  
40883  Polyphase Duplex  10"
Wood  K, A, [ B, S, T, CI, ] D, L &
DF, [ CF, CIF, C, ] D Improved glass indicator  CLICK for BIGGER PIC 
40883S  Polyphase Duplex  10"
Wood  K, A, [ B, S, T, CI, ] D, L &
DF, [ CF, CIF, C, ] D Improved glass indicator, leather case  Magnifier and fitted case! CLICK for BIGGER PIC 
40885  Polyphase Duplex  20"
Wood  K, A, [ B, S, T, CI, ] D, L &
DF, [ CF, CIF, C, ] D Improved glass indicator  
40885S  Polyphase Duplex  20"
Wood  K, A, [ B, S, T, CI, ] D, L &
DF, [ CF, CIF, C, ] D Improved glass indicator, leather case  
40903  Log Log Trig Duplex  10"
Wood  LL0, A, [ B, K, CI, ] T, S1, S2
L, LL1, DF, [ CF, CIF, C, ] D, LL3, LL2 Improved glass indicator. Trig scales degrees and minutes.  
40903S  Log Log Trig Duplex  10"
Wood  LL0, A, [ B, K, CI, ] T, S1, S2 &
L, LL1, DF, [ CF, CIF, C, ] D, LL3, LL2 Improved glass indicator, leather case. Trig scales degrees and minutes.  
40913  Log Log DeciTrig Duplex  10"
Wood  LL0, A, [ B, K, CI, ] T, S1, S2 &
L, LL1, DF, [ CF, CIF, C, ] D, LL3, LL2 Improved glass indicator,. Trig scales in degrees and decimals of degrees.  
40913S  Log Log DeciTrig Duplex  10"
Wood  LL0, A, [ B, K, CI, ] T, S1, S2
L, LL1, DF, [ CF, CIF, C, ] D, LL3, LL2 Improved glass indicator, leather case. Trig scales in degrees and decimals of degrees.  
40923  Log Log Duplex  10"
Wood  LL0, A, [ B, S, T, C, ] LL3, LL2, LL1 &
K, DF, [ CF, CIF, C, ] D, L Improved glass indicator.  
40923S  Log Log Duplex  10"
Wood  LL0, A, [ B, S, T, C, ] LL3, LL2, LL1 &
K, DF, [ CF, CIF, C, ] D, L Improved glass indicator, leather case.  
N40925  Log Log Duplex  20"
Wood  LL0, A, [ B, S, T, C, ] LL3, LL2, LL1 &
K, DF, [ CF, CIF, C, ] D, L Improved glass indicator.  
N40925S  Log Log Duplex  20"
Wood  LL0, A, [ B, S, T, C, ] LL3, LL2, LL1 &
K, DF, [ CF, CIF, C, ] D, L Improved glass indicator, leather case. 
40933  Log Log Vector Duplex  10"
Wood  Sh1, Sh2, Th, [ SI1, SI2, TI, ] D, S, T &
L, LL0, DF, [ CF, B, CI, C, D, ] LL3, LL2 Improved glass indicator, circular & hyperbolic functions.  CLICK for BIGGER PIC 
40933S  Log Log Vector Duplex  10"
Wood  Sh1, Sh2, Th, [ SI1, SI2, TI, D, ] S, T &
L, LL0, DF, [ CF, B, CI, C, ] D, LL3, LL2 Improved glass indicator, circular & hyperbolic functions, leather case.  Hyperbolic Scales! CLICK for BIGGER PIC 
40935  Log Log Vector Duplex  20"
Wood  Sh1, Sh2, Th, [ SI1, SI2, TI, ] D, S, T &
L, LL0, DF, [ CF, B, CI, C, ] D, LL3, LL2 Improved glass indicator, circular & hyperbolic functions.  
40935S  Log Log Vector Duplex  20"
Wood  Sh1, Sh2, Th, [ SI1, SI2, TI, ] D, S, T &
L, LL0, DF, [ CF, B, CI, C, ] D, LL3, LL2 Improved glass indicator, circular & hyperbolic functions, leather case.  
4094  Mannheim Merchant's  10"
Wood  DF, [ CF, CI, C, ] D, rulers,
improved glass indicator  Click here for Bigger Pic Click here for Other Side 
40951S  Merchant's Duplex  5"
Wood  DF, [ CF, C, ] D &
[ CI, ] D frameless glass indicator, leather case  
40953  Merchant's Duplex  10"
Wood  DF, [ CF, C, ] D
[ CI, ] D improved glass indicator.  
40953S  Merchant's Duplex  10"
Wood  DF, [ CF, C, ] D &
[ CI, ] D
improved glass indicator, leather case.  
N4096  Mannheim Desk Slide Rule  20"
Wood  DF, [CF, CI, C, ] D
improved glass indicator, metal stands, leatherette covered hard case.  
4097B  Mannheim
EverThere  5"
Xylonite  DF, [ CF, CI, C, ] D &
back rulers, improved glass indicator, very light weight, leather sheath.  
4097C  Mannheim
EverThere  5"
Xylonite  A, [ B, CI, C, ] D, K &
[ S, L, T ] on reversible slide, back rulers, improved glass indicator, very light weight, leather sheath.  Large View 
4097D  Mannheim
EverThere  5"
Xylonite  A, DF, [ CF, CI, C, ] D, K &
B, [ S, L, T ] on reversible slide, back cm/inch rulers, improved glass indicator, very light weight, leather sheath.  
4098  Mannheim
Pocket Slide Rule  5"
Xylonite  A, [ B, C, ] D &
[ S, L, T ] on reverse of slide, back rulers, frameless xylonite indicator, very light weight, leather sheath.  
N4100  Mannheim
Stadia  10"
Wood  R, H, HC, V, A
side ruler, A & B scales on reverse of slide, improved glass indicator, for survey work
 
N4100S  Mannheim
Stadia  10"
Wood  R, H, HC, V, A
side ruler, A & B scales on reverse of slide, improved glass indicator, leather case, for survey work  
N4101  Mannheim
Stadia  20"
Wood  R, H, HC, V, A
side ruler, A & B scales on reverse of slide, improved glass indicator for survey work.  
N4101S  Mannheim
Stadia  20"
Wood  R, H, HC, V, A
side ruler, A & B scales on reverse of slide, improved glass indicator, leather case, for survey work.  
N4102  Surveyor's Duplex  20"
Wood  D, Sind, Coslah, C, Tan, Tan1, Az &
Vert1, A, [ B, CI, C, ] D, Vert2 improved glass indicator, for surveying.  
N4102S  Surveyor's Duplex  20"
Wood  D, Sind, Coslah, C, Tan, Tan1, Az &
Vert1, A, [ B, CI, C, ] D, Vert2 improved glass indicator, leather case, for surveying.  
N4133S  Mannheim Roylance Electrical  8"
Wood  A, [ B, CI, C, ] D, K &
side ruler, side wire gauge, improved glass cursor, multiple hairlines, special rule marks, leather case.  
N4135S  Power Computing Duplex  5"
Wood  A, [ B, CI, C, ] D
P, R, W, D, for steam, gas and oil engines, frameless glass indicator, leather sheath.  
4139  Duplex Cooke Radio Rule  10"
Wood  LC, A, [ B, T, ST, S, ] D, DI &
L, DF, [ CF, CIF, CI, C, ] D, 2pi improved glass cursor, special electronics scales, hard case. 
41501  Mannheim
 5"
Ivorite  DF, [ CF, CI, C, ] D, L
blank on reversible slide improved plastic indicator, very light weight, leather sheath.  
41531  Mannheim
 5"
Ivorite  A, [ B, CI, C, ] D, K
[ S, L, T ] on reversible slide improved plastic indicator, very light weight, leather sheath.  
4160  Chemist's Duplex  10"
Wood  CI, [ D, Bought, ] Given &
C, [ D, Bought, ] Given improved glass cursor, for chemical analysis.  
4160S  Chemist's Duplex  10"
Wood  CI, [ D, Sought ] Given &
C, [ D, Bought, ] Given improved glass cursor, leather case, for chemical analysis.  
41611  Mannheim
 5"
Ivorite  K, DF, [ CF, L, CI, C, ] D, A
[ T, ST, S, ] C on reversible slide improved plastic indicator, very light weight, leather sheath.  CLICK for BIGGER PIC CLICK for BIGGER PIC 
41613  Mannheim
Slide Rule  10"
Ivorite  K, DF, [ CF, L, CI, C, ] D, A &
[ T, ST, S, ] C on reversible slide improved plastic indicator, very light weight, leatherette sheath. 
CLICK for BIGGER PIC 
4168 also 681555  Duplex
Doric  5"
Ivorite  DF, [ CF, CI, C, D, ] L &
K, A, [ B, ST, S, ] D, T improved glass indicator, leather sheath.  
4175  Kurtz Psychometric  10"
Wood  Special air conditioning scales, improved glass indicator, formulas on reverse.  
41811  Log Log Duplex  5"
Ivorite  LL02, LL03, DF, [ CF, CIF, CI, C, ] D, LL3, LL2 &
LL01, L, K, A, [ B, T, SRT, S, ] D, DI, LL1 Improved cursor, leather case. See also 681287 for later release of the same rule. Note that several cosmetic variations exist, with all black, and black and red scales.  CLICK for bigger PIC! CLICK for OTHER SIDE! 
41813  Log Log Duplex  10"
Ivorite  LL02, LL03, DF, [ CF, CIF, CI, C, ] D, LL3, LL2
LL01, L, K, A, [ B, T, SRT, S, ] D, DI, LL1 Improved cursor, leather case. See also 681251 for later release of the same rule. 

4185A  Magnifying Cursor  Glass  for 4031  
4185B  Magnifying Cursor  Glass  for 40354088, 4094, 40953, 4096, 4100, 4101, 4133, 4165  
4185C  Magnifying Cursor  Glass  for 40884093, 40955, N4096, 4102, 41424175 
681100  DeciLon ©1947, 1961  10"
Ivorite  Sq1, Sq2, DF, [ CF, CIF, L, CI, C, ] D, Ln0, Ln1, Ln2, Ln3 &
Ln3, Ln2, Ln1, Ln0, A, [ B, T, SRT, S, C, ] D, DI, K Improved plastic cursor, leather case.  CLICK for BIGGER PIC 
no number  DeciLon ©1947, 1961  10"
Ivorite  Sq1, Sq2, DF, [ CF, CIF, L, CI, C, ] D, Ln0, Ln1, Ln2, Ln3 &
Ln3, Ln2, Ln1, Ln0, A, [ B, T, SRT, S, C, ] D, DI, K Improved plastic cursor, leather case. Final Decilon production, no model number or grip lines on slide.  CLICK for bigger PIC! CLICK for OTHER SIDE! 
681130  DeciLon ©1947, 1961  5"
Ivorite  Sq1, Sq2, DF, [ CF, CIF, L, CI, C, ] D, Ln0, Ln1, Ln2, Ln3 &
Ln3, Ln2, Ln1, Ln0, A, [ B, T, SRT, S, C, ] D, DI, K Improved plastic cursor, pocket clip leather case. Pocket sized version of 681100 full size rule.  CLICK for BIGGER PIC 
681210  Log Log Duplex DeciTrig  10"
Wood  LL02, LL03, DF, [ CF, CIF, CI, C, ] D, LL3, LL2 &
LL01, L, K, A, [ B, T, SRT, S, ] D, DI, LL1 Improved cursor, leather case. Appears to be a renumbered 40813 rule.  CLICK for BIGGER PIC 
681215  Log Log Duplex DeciTrig  10"
Wood  LL02, LL03, DF, [ CF, CIF, CI, C, ] D, LL3, LL2 &
LL01, L, K, A, [ B, T, SRT, S, ] D, DI, LL1 Improved cursor, leather case. Appears to be a renumbered 40813 rule, complete with sewn leather case, in a set, the rule is still numbered 681210.  
681251  Log Log Duplex DeciTrig  10"
Ivorite  LL02, LL03, DF, [ CF, CIF, CI, C, ] D, LL3, LL2 &
LL01, L, K, A, [ B, T, SRT, S, ] D, DI, LL1 Improved cursor, leather case. Seems to be newly numbered 41813 rule in every respect.  CLICK for bigger PIC 
681287 681261 with leather clip case  Duplex DeciTrig Jetlog Jr.  5"
Ivorite  LL02, LL03, DF, [ CF, CIF, CI, C, ] D, LL3, LL2 &
LL01, L, K, A, [ B, T, SRT, S, ] D, DI, LL1 Improved unbreakable cursor, leather case. Seems to be newly numbered 41811 rule in every respect.  
681400 Analon 
Analon engineering constant rule  10"
Ivorite 
V2, V1/2, A, [ B, U1/2, U1, C, ] D, V, V1
Improved unbreakable cursor, leather case, special manual. Completely unique rule and scale design, with pysical constants on the scales.  
681497 40703 with decimal trig scales  Duplex
Polyphase Duplex Decitrig  5"
Wood  Front  DF, [ CF, CIF, CI, C, ] D, L Back  K, A, [ B, T, SRT, S, ] D, DI improved unbreakable indicator, leather sheath.  Wood Edged Rule CLICK for BIGGER PIC 
681555 also 4168  Duplex
Polyphase Duplex Decitrig  5"
Ivorite  DF, [ CF, CI, C, ] D, L &
K, A, [ B, ST, S, ] D, T improved unbreakable indicator, leather sheath.  
681565  GP12  10"
Ivorite  Sq1, Sq2, DF, [ CF, T, SRT, S, CI, C, ] D, A, K &
cm, inch rules, number to log converter, inch/cm converter. Conversion factors plastic cursor, black and red scales, green plastic body supports, black leather case. Very nice but seldom seen late production rule.  CLICK for bigger PIC 
681586
 Simplex
Modern Polyphase  5"
Ivorite  K, DF, [ CF, L, CI, C, ] D, A &
[ T, ST, S, ] C improved unbreakable indicator, leather sheath.  
681607 Same as 40535  Mannheim Polyphase  20"
Wood  inch A, [ B, CI, C, ] D, K, cm [ S, L, T ] improved glass indicator, wood back. green leather flap case  CLICK for BIGGER PIC CLICK for BIGGER PIC! CLICK for BACK 
681608 Same as 40535  Mannheim Polyphase  20"
Wood  inch A, [ B, CI, C, ] D, K, cm [ S, L, T ] improved glass indicator, wood back. green leather flap case 
CLICK for bigger PIC! CLICK for bigger PIC! 
681617 Same as 40533S  Mannheim Polyphase  10"
Wood  inch A, [ B, CI, C, ] D, K, cm [ S, L, T ] improved glass indicator, late production, Xylonite back. sewn leather case  Click here for Bigger Pic Click here for Other Side 
681648
 Simplex
Polyphase  5"
Ivorite  A, [ B, CI, C, ] D, K &
[ S, L, T ] improved unbreakable indicator, leather sheath.  
681749  Mannheim Desk Slide Rule  20"
Wood  DF, [ CF, CI, C, ] D
improved glass indicator, metal stands, leatherette covered hard case.  
681791
 Simplex
Merchants  5"
Ivorite  DF, [ CF, CI, C, ] D, L
improved unbreakable indicator, leather sheath.  
681892  K12 Prep  10"
PVC  K, A, [ B, S, CI, T, C, ] D, L student slide rule plastic cursor, green scales, green plastic body supports, plastic pouch.  
Mannheim rule        
Mannheim rule        
Old Pocket Mannheim rule      shows extra magnifying cursor added.  
Duplex rule        
Duplex rule        
Duplex rule        
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