Pickett & Eckel Model 2 Deci Log Log Duplex Slide Rule

This 10-inch duplex slide rule is made from a magnesium alloy coated with white celluloid. It has a flat glass indicator with metal sides and stainless steel end posts. One screw on the back bottom side is missing. The top side is engraved with a serial number: CO24920.
The front of the rule has nine D scales, four also labeled 1/N, one also labeled Co, and four also labeled N. The two groups of four scales are extended and folded, so that for reading off logarithms, the rule is the equivalent of a rule 80" long. The slide has CF, CI, and C scales.
The slide has several markings above the scales. The first marking reads: INTERNATIONAL (/) COPYRIGHT 1947 (/) U.S.A. COPYRIGHT 1947 (/) R. C. PICKETT, A. F. ECKEL (/) CHICAGO, U.S.A. Second, there is a table for Digits or Zero for Sine and Tangent and a table for the number of digits in a result found on the C scale. Third, a logo inside an oval reads: DECI• (/) LOG LOG (/) Trade Mark. Fourth is another table for whether a result has zeroes or digits in results for squares, cubes, and roots. The fifth marking reads: THE NUMBER OF ZEROS IS (/) ONE LESS THAN THE ABSO- (/) LUTE VALUE OF THE NEGA- (/) TIVE CHARACTERISTIC. (/) EXAMPLE: 10-5 = .00001. The sixth marking reads: THE NUMBER OF DIGITS IS (/) ONE GREATER THAN THE (/) POSITIVE CHARACTERISTIC. (/) EXAMPLE: 105 = 100,000. Finally, a mark at the right end of the slide reads: PATENTS PENDING (/) MADE IN U.S.A. (/) PICKETT & ECKEL, INC. (/) CHICAGO 3, U.S.A. (/) MODEL 2.
The back of the rule has three cube root scales, an L scale, a D scale, and two square root scales. The scales for roots are folded, so that the rule is the equivalent of 60" in length for cube roots and 20" in length for square roots. The slide has two T scales and ST, S, CI, and C scales. The left side of the slide is marked: INTERNATIONAL (/) COPYRIGHT 1945 (/) U.S.A. COPYRIGHT 1945 (/) R.C. PICKETT, A. F. ECKEL (/) CHICAGO, U.S.A.
Arthur Frederick Eckel (1894–1960) and Roswell Colvert Pickett (1892–1969) partnered in Chicago in 1943 to manufacture slide rules. By 1946, they had transitioned from paper slide rules to magnesium, and Pickett established a branch of the company in Alhambra, Calif. In 1947, Maurice L. Hartung, a University of Chicago professor who helped Pickett & Eckel market their products to schools, described the Model 2 in How to Use the Deci-Log Log Slide Rule (Chicago: Pickett & Eckel, 1947). A copy of this pamphlet is 1979.0601.04. Eckel received four of the patents mentioned as "pending" on the object in 1948 and 1949. He left the company around that time, and his name was removed from slide rules by 1950. Thus, this example was probably made between 1946 and 1950.
Indeed, the donor, Frank M. Graves, reported that he used this rule as a college student. He received a Bachelor of Science degree in chemistry from Syracuse University in 1949.
The rule fits in a brown leather case marked on the flap with "Pickett" in script over a triangular logo. A belt loop on the back of the case is marked: SADDLE (/) LEATHER. The logo was used by the company from 1950 to 1958, so the case may be a replacement. The style of the belt loop, though, differs from the ring construction depicted in Pickett's 1953 catalog. In 1953, Model 2 and its case sold for $21.35.
References: Arthur F. Eckel, "Decimal Point Locator for Slide Rules" (U.S. Patent 2,446,696 issued August 10, 1948), "Calculator and Decimal Point Locator (U.S. Patent 2,466,883 issued April 12, 1949), "Slide Rule," (U.S. Patent 2,466,983 issued April 12, 1949), "Interchangeable Scale for Slide Rules" (U.S. Patent 2,491,650 issued December 20, 1949); Pickett All-Metal Slide Rules and "Retail Price List-Catalog," (Chicago: Pickett & Eckel, February 1, 1953); International Slide Rule Museum, "Pickett All-Metal Slide Rules," http://sliderulemuseum.com/SR_Dates.htm#Pickett; Accession File.
Currently not on view
Currently not on view
Object Name
calculating rule
slide rule
date made
Pickett & Eckel, Incorporated
Physical Description
magnesium (overall material)
celluloid (laminate material)
glass (cursor material)
leather (case material)
overall: 1.8 cm x 33.3 cm x 8 cm; 23/32 in x 13 1/8 in x 3 5/32 in
place made
United States: Illinois, Chicago
ID Number
catalog number
accession number
Rule, Calculating
See more items in
Medicine and Science: Mathematics
Science & Mathematics
Slide Rules
Data Source
National Museum of American History, Kenneth E. Behring Center


"I have this slide rule and I believe the cursor is made of a polymer, possibly PMMA (Acrylic) or other."

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