**Otis King Type L**

The Otis King calculator was sold into the 1970s and was advertised in competition with the early electronic hand-held calculators, so is included as a comparison with the electronic calculators with which it competed.

Otis King calculator extended.

**Otis King Model L.**

**Distinctive features:** Cylindrical slide rule.

**Technical details:**Although described as a calculator (see top photograph) this is really a cylindrical slide rule. By forming it as a cylinder the effective length of the slide rule
scale is 66 inches long.

153 mm closed, 262 mm extended, x 31 mm diameter

(6" closed, 10.3" extended, x 1.25" diameter).

"British made throughout".

Carbic Limited,

171, Seymour Place,

London.

There were two versions of this calculator - the Model K and the Model L which had an additional scale for determining logarihms.

An advertisement for the model L in February 1971 gives a price of 85s (£4-25p [about $10-50]), which was a fraction of the cost of an electronic calculator (see Bowmar 901B/Commodore C110 at £79 [approx. $195]).

One of the last
advertisements for an Otis King calculator (actually the model K) in August 1973 gives a price of £4-65p [about $11-50], which was now comparable to the cost of the cheapest electronic calculator.

The story of Otis King calculators is told in "Otis King Calculators: A History of Production, 1919-1977", by and published by Colin Barnes, ISBN 0 9535039 0 9 - see the United Kingdom Slide Rule Circle's site at http://www.uksrc.org.uk/publications2015.pdf.

Otis King calculator closed

Otis King calculator extended

Otis King calculator, closed in its box.

*The Otis King calculators were popular for many years and continued to sell into the era of electronic calculators due to their very low cost.*

**Hand-held Calculators**

*Vintage Calculators *

Text & photographs copyright, except where stated otherwise, © Nigel Tout 2000-2024.