Pickett 904-ES Decimal Keeper Duplex Slide Rule

Pickett 904-ES Decimal Keeper Duplex Slide Rule

Usage conditions apply
This aluminum duplex slide rule has a yellow coating and a clear plastic indicator. The "ES" in the model number refers to the rule's "Eye Saver" yellow color. The rule and indicator are held together with aluminum braces that have protruding grooves. The front of the rule has K, A, DF, D, and L scales, with CF, S, T, CI, and C scales on the slide. The scales are 9-1/2 inches long. The back of the rule has a D* scale, with T*, S* Cl*, and C* scales on the slide. Instead of covering the typical one decade of C and D scales, the scales with asterisks cover twenty decades, from 1010 to 10-10. These scales helped inexperienced users keep track of the decimal point. They performed their calculation first on the back, to determine the order of magnitude, and then a second time on the front, to make the answer precise to three significant figures.
The front of the slide is marked: MODEL 904-ES (/) TRIG AND (/) DECIMAL KEEPER (/) SPEED RULE. A Pickett logo is at the other end of the slide, with the number 47 printed above the logo. The back of the rule is marked: PATENT (/) APPLIED FOR; DECIMAL KEEPER; PICKETT & ECKEL, INC. (/) CHICAGO 3, ILL. - ALHAMBRA, CAL. The logo on this rule is that used by Pickett from 1958 to 1962. The shape and material of the cursor and the braces suggest a date of 1957–1959. Hence, the object appears to have a rough date of 1958–1959.
The donor patented an "automatic decimal point slide rule" and assigned the patent to Pickett. He also distributed Pickett slide rules through his own mail order firm of Devonics, Inc.
The rule was received in a plastic bag. For somewhat related documentation, see 1995.0126.04. See also Lawrence J. Kamm, "Automatic Decimal Point Slide Rule" (U.S. Patent 2,893,630 issued July 7, 1959).
References: Dieter von Jezierski, Slide Rules: A Journey Through Three Centuries (Mendham, N.J.: Astragal Press, 2000), 75–76, 100; Ron Manley, "Pickett 904-ES – Trig and decimal keeper," http://www.sliderules.info/collection/10inch/090/1096-pickett-904.htm; "Slide Rule Dates and Time-Lines," http://sliderulemuseum.com/SR_Dates.htm.
Currently not on view
Object Name
calculating rule
slide rule
date made
ca 1958-1959
Pickett & Eckel, Incorporated
place made
United States: California, Alhambra
Physical Description
aluminum (overall material)
plastic (cursor material)
overall: 1 cm x 31.2 cm x 5 cm; 13/32 in x 12 9/32 in x 1 31/32 in
ID Number
accession number
catalog number
Credit Line
Gift of Lawrence J. Kamm
General Calculation
Rule, Calculating
See more items in
Medicine and Science: Mathematics
Science & Mathematics
Slide Rules
Data Source
National Museum of American History
Nominate this object for photography.   

Our collection database is a work in progress. We may update this record based on further research and review. Learn more about our approach to sharing our collection online.

If you would like to know how you can use content on this page, see the Smithsonian's Terms of Use. If you need to request an image for publication or other use, please visit Rights and Reproductions.


Add a comment about this object