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CIRCULAR SLIDE RULE ARCHIVE

Circular rules from every maker are shown here, including Hemmi, Aristo, Concise and others. As we collect scale data and photos on new circular rules, they will get added into the archive as time permits.

Often, original makers became obscured as the rules were frequently re-sold by other companies. SINCO (Scientific Instruments Co.) made rules under its own name, as well as most of the more sophisticated circular rules for Pickett such as the 110ES and 111ES. Gilson made its rules, especially the Midget, with no name printed on them (not even Gilson), and they were then resold by POST, Dietzgen, Lietz and others as their own product.

Concise circular rules were often sold in the USA with Company logos and markings, as promotional items due to the interesting marketing strategy of Sama & Etani. This sometimes confuses neophyte collectors into thinking they have found a unique rule, when it is merely a house-marked Concise brand slide rule made for advertising reasons, that says 3M, Garrett, DOW, Shell, So-and-so Heating, etc. Many of these circular slide rules with special data charts and metric conversion data were designed and marketed by Sama & Etani in North America, but manufactured by Concise in Japan, further confusing matters as to the real origin of the slide rule. Mr. Sama and Mr. Etani dreamed up the idea of the data chart rules, and metric factors designs as part of their business school thesis, speculating they might be able to sell 30,000 pieces. They wound up selling more than a million units, and their logo-marked rules were incredibly popular and widely used in many industries as promotional items.

They designed a very interesting circular rule, the Data Center, which was rectangular, had a circular rule on the face, rulers along the sides, conversions to periodic tables on the rear face, and a pull-out double-sided data card that had industry specific information. This rule appears in many variations for many different end customers, but they are all Concise manufactured rules from the same exact place. Interestingly, manufacture of the Data Center that had a periodic table was discontinued due to complaints from teachers, who said that students were using them to cheat on exams. As a result, this very useful pocket reference tool was lost to everybody. Concise rules were also re-branded and sold by Fullerton, Lafayette and numerous other companies, in addition to the special designs created by Sama & Etani.

Circular rules often employed a slip clutch and dual cursor design, since the scales were frequently stationary on one disk, such as the Pickett 101C, and Gilson Midget and Atlas. A few more advanced rules from SINCO and Concise in Japan, and Aristo in Germany have very complex rotating disk designs and work more like a conventional slide rule. Whether it was the physical operation or other factors, straight rules outsold circular ones by about 10:1, and there are not very many circular rules in most model line ups, except Concise, which seemed to make only circular rules.

Circular rules offer greater effective scale length in a smaller physical package, so that you don't poke the guy at the next desk in the eye with that 20 inch straight rule in your quest for better resolution and accuracy. Concise circular rules also added some interesting 'look-up' and conversion features to the basic rule for added utility, like the famous Science Center. Circulars come in plastic and metal construction (plus paper when made as perrygrafs), but not normally in wood. Sizes ranged from the very small (1.5 inch) to the fairly massive, like the 8 inch Gilson ATLAS/Binary rule.

The ARCHIVE will appear below shortly!

CONCISE Circular Slide Rules

MODEL	INFO / SCALES	IMAGE
CONCISE Model 28N	A compact 80mm/3 1/4 inch pocket circular slide rule, with conversion factors and formulas on rear face. Very nice rule, complete with vinyl slip case and manual. This is a powerful lightweight pocket rule, with performance equal to a much larger straight rule. Rotating cursor and disk. (5 Scales + Formulas) Front - D, C, CI, A, K Back - Conversions and formulas	CLICK for BIGGER PIC! CLICK for BACK PIC!
MODEL	INFO / SCALES	IMAGE
CONCISE Model 32	An amazing and tiny patented (479446) 2 inch diameter pocket circular slide rule with Perpetual Calendar, covering 1960 to 1981 (to me, this is not perpetual, but GREAT for fixing historical dates and days). Basic Rule on outside ring has C and D scales, inner windows and grid do dates and days. White plastic rule, complete with attached vinyl slip case and manual. This is a very unusual rule from Concise. Rotating disk, back is blank. CLICK HERE to get Calvin Fan's method for extending the range of the 'perpetual calendar' to 2018. (2 Scales + Calendar) Front - D, C, Date decoder Back - Blank	CLICK for BIGGER PIC!
MODEL	INFO / SCALES	IMAGE
CONCISE Model 90	A compact 90mm pocket circular slide rule, with conversion factors and formulas on rear face, and a temperature conversion scale. Very nice rule, complete with vinyl slip case and manual. This is a perfect lightweight pocket rule, with performance equal to a much larger straight rule. Rotating cursor and disk. CLICK HERE for reverse view. (8 Scales + Temp) Front - L, D, C, CI, A, K, S, T Back - Conversions and formulas, temperature scale	Click for BIGGER PIC! Click for BIGGER PIC!
MODEL	INFO / SCALES	IMAGE
CONCISE 200 Electrical Engineering Data Center	An amazing 60mm pocket circular slide rule, with inch and cm rulers, a complete reactance nomograph on the back, and a double sided pull out card with physical constants, formulas and conversions, plus COLOR CODES, wire gauges, etc.. An electronics textbook in your pocket. (8 Scales) Front - D, C, CI, L, A, S, T, K + 2 rulers Back - Reactance Nomograph, plus pull out data card	Click for BIGGER PIC
MODEL	INFO / SCALES	IMAGE
CONCISE Model 260	A powerful 4 inch duplex circular slide rule, with dual rotating faces. Very nice rule, complete with vinyl slip case and manual. This is a general purpose rule with performance equal to a much larger straight rule. Rotating cursor and 2 disks. (10 Scales) Front - D, C, CI, A, K Back - D, S, T, S&T, L	CLICK for BIGGER PIC! CLICK for BACK PIC!
MODEL	INFO / SCALES	IMAGE
CONCISE Model 270	A powerful 4 inch duplex circular slide rule, with dual rotating faces. Very nice rule, complete with vinyl slip case and manual. This is a trig enhanced rule with performance equal to a much larger straight rule. Rotating cursor and 2 disks. Pic is actually a 271, which is very similar to the 270, except for two trig scales. (12 Scales) Front - L, D, C, CI, A, K Back - DI, D, S, TI1, TI2, ST	Actually a 271 CLICK for BIGGER PIC! CLICK for BACK PIC!
MODEL	INFO / SCALES	IMAGE
CONCISE Model 271	A powerful 4 inch duplex circular slide rule, with dual rotating faces. Very nice rule, complete with vinyl slip case and manual. This is a trig enhanced rule with performance equal to a much larger straight rule. Rotating cursor and 2 disks. (12 Scales) Front - L, D, C, CI, A, K Back - DI, D, SI, TI1, TI2, SI/TI	CLICK for BIGGER PIC! CLICK for BACK PIC!
MODEL / PRICE	INFO / SCALES	IMAGE
CONCISE Model 300 Advanced Circular Rule	A large format 4 1/4 in. pocket circular slide rule with dual rotating disks (each side), log log and extended trig scales. Excellent quality compact rule with more advanced functions. complete with black vinyl case and general manual. (15 Scales) Front - K, A, D, [ C, CI, B, L ] Back - LL3, LL2, D, [ C, S, T1, T2, ST ]	Click for BIGGER PIC! Click for BIGGER PIC!
MODEL	INFO / SCALES	IMAGE
CONCISE Model 380 Radio Computer	An amazing 110mm/4 1/2 inch pocket circular slide rule, with extensive duplex electronics calculating functions. This rule computes L/C/Frequency/dB/Reactance/Wavelength/Power ratio. Very rare, seldom seen in North America, a must have rule for electronics professionals. (14 Scales!) Front - C, L, F, Xc, Freq., Lambda, Fcs Back - C, L, F, X, dBw, dBv, XL	CLICK for BIGGER PIC! CLICK for BACK PIC!
MODEL	INFO / SCALES	IMAGE
CONCISE Model E Weights and Measures Conversion Table	A unique pocket data center and circular slide rule, with extensive unit conversion functions, including ri, acres, litres, carats, chains, tubo, miles, ken, grams, grains, meters, ounces, koku, cubic inches, and MUCH MORE. This double sided data center has conversion factors for all units, which are then entered into the circular rule for your measurement. Great for people that travel or work with international units, especially in Asia or Europe. (5 Scales, and 59 units!) Front - D, C, CI, A, K Data Center - 59 units, weight, length, square, cubic capacity

Hemmi/Sun Circular Rules

SLIDE RULE	INFO / SCALES
Hemmi/Sun Circular 1001 CLICK for BIGGER PIC!	Pocket Square/Circular Rule A compact 75mm/3 inch pocket square body, circular scale slide rule, with an unusual blue/green body scale, and a white rotating scale with finger grips along the outside edge. Virtually unknown here in North America, this Hemmi circular rule is very attractive and functional, with a very striking blue/green color scheme. Constructed of several layers of plastic, overlaid and riveted in the corners. This is a simple lightweight pocket rule, with performance equal to a much larger straight rule, blank on the rear. Came complete with vinyl case and manual. (5 Scales) Front - A, D, C, CI, L
SLIDE RULE	INFO / SCALES
Hemmi/Sun Circular 1002 CLICK for BIGGER PIC!	Pocket Circular Rule A compact 75mm/3 inch pocket circular slide rule, with an unusual blue circular rotating scale. Virtually unknown here in North America, this Hemmi plastic circular rule is very attractive and functional, with a very striking blue color scheme. This is an attractive lightweight pocket rule, with performance equal to a much larger straight rule. Rotating cursor and disk, blank on the rear. Came complete with vinyl case and manual. (4 Scales) Front - A, D, C, CI

PICKETT Circular Rules

MODEL	INFO / SCALES	IMAGE
PICKETT Model 101C	4 Inch Duplex Circular Pickett's most popular aluminum circular slide rule, with decimal to fraction conversions and additional scales on rear face. Very nice rule, complete with vinyl slip case and manual. This is a powerful lightweight pocket rule, with performance equal to a much larger straight rule. Rotating dual cursors on one side (with scales ID's on cursor), single on other. Note, vinyl slip and manual are a bit worn, this is an early uncommon release of this rule (1957), which includes unique fractional scales (Af and Fa). (15 Scales + conversions) Front - C, CI, A, Af, L, Fa, LL1, LL2, DS, DT, M K Back - C, S, ST, T, Conversions	CLICK for BIGGER PIC! CLICK for BACK PIC!
MODEL	INFO / SCALES	IMAGE
PICKETT Model 101C	4 Inch Duplex Circular Pickett's most popular aluminum circular slide rule, with decimal to fraction conversions and additional scales on rear face. Very nice rule, complete with early style (riveted) leatherette slip case and original Pickett manual. This is a powerful lightweight pocket rule, with performance equal to a much larger straight rule. Rotating dual cursors on one side (with scales ID's on cursor), single on other. Rule and case are in excellent condition. (15 Scales + conversions) Front - C, CI, A, Af, L, Fa, LL2, LL1, DS, DT, M Back - C, S, ST, T, Fractional Conversions	CLICK for bigger PIC! CLICK for OTHER SIDE!
MODEL	INFO / SCALES	IMAGE
PICKETT 104C PROFIT CALCULATOR	Pickett's commercial pricing circular rule, a huge 8" plastic simplex rule. Instructions on the face. One stationary back side, one rotating front disk, and one rotating clear cursor. Very neat and useful slide rule. (4 Scales) Front - Markup, Price, Margin, Discount	Click for BIGGER PIC of RULE
MODEL	INFO / SCALES	IMAGE
PICKETT Model 110ES	5 Inch Log Log Duplex Circular One of the most requested Pickett aluminum circular slide rules, in the popular ES (eye saver) yellow color. Complete with black belting leather case with gold logo, and miniature manual that fits inside the case. Has tracked duplex cursor, (with scale markings), and rotating disks on both sides. The unusual two line cursor permits fast circle area calculations between A and D (set the long cursor on D to the diameter, A will show the area on the short cursor). This is a very powerful pocket rule, with performance equal to a much larger straight rule. Has extended trig scales and log log scales. Has doubled CI scale (EI), linear V1 and V2 scales (for right triangles), G scale for stadia calculations, and extended spiral C and D scales (equivalent to 50 inch length). This rule's unique construction has laminated engraved and filled plastic bodies on a metal core for mechanical strength and very long wear life. This rule DOES NOT have painted scales like the 101C, it is engraved like a Versalog. The only detracting feature is the previous owner's name neatly inside the flap (Christensen). (12/12 [24 Total] Scales, 2 are spiral) Front - LL3, LL2, LL1, K, A, D, [ C, CI, B, EI ] Back - D (spiral) V2, [ V1, C (spiral), G, T, S, T, S, T, ST, L ]	CLICK for bigger PIC! CLICK for OTHER SIDE!
MODEL	INFO / SCALES	IMAGE
PICKETT Model 111ES	5 Inch Log Log Duplex Circular One of the most uncommon Pickett aluminum circular slide rules, in the popular ES (eye saver) yellow color. Complete with black belting leather case with gold logo, and miniature manual that fits inside the case. Has tracked duplex cursor, (with scale markings), and rotating disk on one side. The unusual two line cursor permits fast circle area calculations between A and D (set the long cursor on D to the diameter, A will show the area on the short cursor). This is a powerful pocket rule, with performance equal to a much larger straight rule. Has extended trig scales and EIGHT log log scales. Has DI scale and doubled CI scale (EI), with six trig scales. This rule's unique construction has laminated engraved and filled plastic bodies on a metal core for mechanical strength and very long wear life. This rule DOES NOT have painted scales like the 101C, it is engraved like a Versalog. The only detracting feature is the previous owner's name neatly inside the flap (Christensen). (10/13 [23 Total] Scales) Front - LL3, LL2, LL1, LL0, K, A, D, [ C, CI, EI ] Back - /LL3, /LL2, /LL1, /LL0, L, DI, D, T, S, T, S, T, ST	CLICK for bigger PIC! CLICK for OTHER SIDE!

Other Circular Rules

MODEL / PRICE	INFO / SCALES	IMAGE
Fearns Calculators Log Log Circular Rule	A larger 5 inch pocket circular slide rule with conversion factors and reference information on the reverse side, from the UK. Has a rotating clear disk with secondary cursor, and rotating cursor on one side, reference data on the other. Unusual 3 turn spiral log log scale. Excellent quality and unique design and construction larger rule from a seldom seen manufacturer, complete with vinyl slip case and original manual. Blue and red scales, black case. (9 Scales, Metric, Conversion + Reference Data) Front - K, C, [ D, B, ] A, LL, S, T, K Back - Metric, Conversion + Reference Data	Click for BIGGER PIC! Click for BIGGER PIC!
MODEL / PRICE	INFO / SCALES	IMAGE
Field's Hydraulics Calculator	Excellent Condition. A larger 6 inch specialty circular slide rule, made by Perrygraf in the USA. This complex cardboard with 3 rotating parts rule was copyrighted in 1950. This is used for hydraulics calulations involving the gravity flow of water in pipes, based on the Manning Formula. Comes complete with the original paper case, and the reverse side has full instructions for use. (9 Scales + Instructions) Front - see pics Back - Operating Instructions	Click for BIGGER PIC!
MODEL	INFO / SCALES	IMAGE
J. SUGIURA Super Slide Rule No. 120	A compact 80mm/3 1/4 inch pocket circular slide rule with very powerful trig functions, and rotating disks on both faces. Very nice rule, complete with vinyl slip case and manual. This rule has trig functions in degrees and seconds, ideal for navigation or as a stadia rule, with performance equal to a much larger straight rule. (12 Scales !) Front - Cos, Sin, A, B, T, C, L Back - R2/P2, R1/P1, S/Q, Theta, R(ST)	CLICK for BIGGER PIC! CLICK for BACK PIC!
MODEL	INFO / SCALES	IMAGE
COMPUTAR	A neat little 4 inch circular rule used to determine camera lens performance/field of view with various different CCD cameras with image areas from 1 inch to 1/4 inch. Plastic front and cursor, cardboard rear section. (4 Scales) Front - Distance, Angle of View, Object dimensions, Focal Length Back - Directions	Click for BIGGER PIC of RULE
MODEL	INFO / SCALES	IMAGE
RCAF Paratrooper's Rule	Massive 7 inch diameter circular slide rule, with all functions for computing a parachute drop. Very nice rule, was brand new in MIl-packaging, was opened to take the pic only A truly fascinating rule. BRAND NEW, instructions on front face, back is blank. (4 major scales + 4 minor scales) Front - Wind Speed (kts or mph), Height (feet), Drift Distance (yards), Vertical Velocity, T7 index, T10 index, G11 index, G12 index, K Back - Blank	CLICK for BIGGER PIC!
MODEL	INFO / SCALES	IMAGE
Gilson Midget	A very famous American 4 inch pocket circular slide rule, with both fractional converters and conventional scales. Very nice rules, complete with very used slip cases (old names inside, sorry) and manuals. This rule was sold by many people, inclduing Lietz, POST, and Dietzgen, and doesn't even have Gilson's name on it. One side copyright 1931, one side 1936, this is one of th emost durable designs ever made. This rule can add and subtract fractions, convert to fractional answers, display drill sizes in MM and inches, and many other fascinating tricks. White coated metal body, twin cursors on one side, single on the other. (20 Scales) Front - 3 sets degrees, sines, tans, fract/decimals Back - C, CI, L, A, Binary, LL, Fract, Drill, Thread, MM	CLICK for BACK PIC!
MODEL	INFO / SCALES	IMAGE
GILSON Lietz Binary	8 Inch Duplex Circular Gilson's most famous aluminum circular slide rule, with alternating yellow/white stripes and fractional converter/operator scales. This rule was made by Gilson (copyright 1940), but sold by numerous other companies, this one has the Lietz manual included, and was sold as a Lietz Binary Rule. This is a very powerful rule, with 3 sets of trig scales (sin/tan), giving performance equal to a much larger straight rule. Coupled with the degrees/minutes format, this high resolution is ideal for navigation or other survey uses. Has many unique scales such as drill and thread plus fractional 'binary' scales that permit operations directly with fractional numbers. Rotating dual cursors/clutch on one side, single cursor on other. (21 Scales !) Front - C, CI, A, K, L, Log Log (1.0015-1,000,000), fractions, fractions, drill/thread, mm Back - degrees, sines, tans, degrees, sines, tans, degrees, sines, tans, Fractional Conversions	CLICK for bigger PIC! CLICK for OTHER SIDE!
MODEL / PRICE	INFO / SCALES	IMAGE
Nautical Mark 1 Slide Rule FNS-3 G. Felsenthal and Sons	Massive 8 inch diameter circular slide rule, with functions for computing time, speed and distance. Very nice rule, copyright 1955, also marked N140-155s-51537B(P), and FNS-3. A very useful rule, no case was included, back is blank. Bureau of ships Mark 1, model 'O'. (6 scales) Front - Speed (kts), Distance (nautical miles, yards), Time (mins., hrs) Back - Blank	CLICK for BIGGER PIC!
MODEL / PRICE	INFO / SCALES	IMAGE
Nautical Slide Rule FNS-3 Weems Sys. of Navigation	Massive 8 inch diameter circular slide rule, with functions for computing time, speed and distance. Very nice rule, very similar to Mark 1, FNS-3. A very useful rule, an envelope case is included and one sheet of instructions, back is blank. (6 scales) Front - Speed (kts), Distance (nautical miles, yards), Time (mins., hrs) Back - Blank	CLICK for BIGGER PIC!
MODEL / PRICE	INFO / SCALES	IMAGE
Electrical Rule T and T Electric Manufacturing Co. The Fast Calculator	The Fast Calculator Copyright 1938 by Frank A. Short, Los Angeles. Made by T and T Electric Manufacturing Co. A fascinating 7 inch long aluminum multi-wheel slide rule for electrical calculations. Purple anodized scales on aluminum, it does wire sizing, current and drop calculations. The reverse side does motor sizing calculations. 4 rotating wheels total. Very high quality construction, self documenting design with all instructions on the rule body. Has a soft leather slip case. (5 Scales, 1 chart on one side, 2 ea. 5 scale selectors on reverse) Front - Wire Sizing/Drop Back - Motor Sizing	CLICK for bigger PIC! CLICK for bigger PIC!

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