The object illustrated is a slide rule for carrying out complex mathematical calculations. The first slide rule was made in the 17th century in England by William Oughtred. The model 2664, shown here, was made between 1955 and 1965 in Japan by The Hemmi Bamboo Slide Rule Company Ltd. The company was founded in 1895 and is the oldest and best known Japanese manufacturer of slide rules. In 1912 the company was granted Japanese Patent No. 22129 for its laminated bamboo construction method for slide rules.
The slide rule has two parts which display figures: the body and a central section which slides. Then over both is a cursor. Whereas the body and the slide are marked with scales, the main purpose of the cursor is to enable the accurate alignment of figures which are not immediately adjacent. To achieve this, the cursor has a central hairline, as can be seen in the images.
The model 2664 has on the top and bottom edges length measured in inches and centimetres. This shows that the rule is ten inches long. On the reverse of the slide is a set of conversion tables and other mathematical information. The blue ink splodges, suggest the rule was used by a schoolboy using a fountain pen, rather than an architect, engineer or designer.
Slide rules were made in many different sizes and with scales for different mathematical, scientific, commercial, industrial and military purposes. Though now superseded by calculators and computers, slide rules can be a useful teaching aid, as users will acquire knowledge of mathematical principles.
There are collectors of slide rules and even a slide rule museum. Having the original box will increase the value of the rule.
Slide rules were used to design the Boeing 747 aircraft and the Apollo 11 rocket used for the moon landing. For those of us who dreaded even arithmetic at school, slide rules are beyond our comprehension, but all users need instructions on how to use particular models. A simple instruction leaflet is illustrated later.