Hemmi-Sun 255 Duplex Slide Rule

This ten-inch bamboo rule is coated on both sides and its long outer edges with white celluloid. The rule is held together with metal posts. The glass indicator has a metal frame with bamboo and celluloid sides. The rule is marked on the base's upper right front corner: SUN (between two drawings of the sun) HEMMI JAPAN CL NO. 255.
Hemmi designed this model for electrical engineers. The front of the base has L, K, DF, D, χ, and θ scales. The front of the slide has CF, CIF, CI, and C scales. The back of the base has Sh1, Sh2, Th, A, D, LL3, LL2, and LL1 scales, with B, TI2, TI1, SI, and C scales on the back of the slide.
The rule is stored in a green rectangular fabricoid and cardboard box which is opened by removing the right end. This end is marked: SUN (between two drawings of the sun) (/) HEMMI BAMBOO (/) SLIDE RULE. There are two stars where the box joins together. Both ends of the box are heavily taped.
After 1950, Hemmi rules were stamped with codes indicating the year and month of manufacture. According to the code on this instrument (CL), it was made in December 1952. The donor reported that he purchased it in Japan in 1955.
Reference: International Slide Rule Museum, "Slide Rule Dates and Time-Lines," http://sliderulemuseum.com/SR_Dates.htm.
Currently not on view
date made
Physical Description
paper (case material)
bamboo (overall material)
plastic (laminate material)
metal (part material)
glass (cursor material)
overall: 2 cm x 33.1 cm x 6.5 cm; 25/32 in x 13 1/32 in x 2 9/16 in
ID Number
accession number
catalog number
Credit Line
Gift of Clyde S. Freint
Engineering, Electrical
See more items in
Medicine and Science: Mathematics
Science & Mathematics
Slide Rules
Data Source
National Museum of American History


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