a slide rule for everyone
For very many years the slide rule has been a standard piece of equipment for engineers, technologists and others working constantly with mathematical problems. The slide rule gives answers to multiplication and division with great rapidity and problems combining multiplication and division can be worked out as easily as straight calculations of either. There is no limit to the number of terms which can be handled and figures seldom need to be written down during the calculation. Today the use of the slide rule is no longer confined to practised mathematicians. As a result of its many advantages the Otis King calculator has brought the slide rule principle of working to every walk of life because:-
simple to use No special training or mathematical knowledge is needed.
quick in use An answer to a multiplication or division problem can be obtained almost as quickly as the figures of the calculation can be spoken. Also there is no complicating diversity of seldom used scales.
accurate It will produce reliable results of up to four or five significant figures.
durable The Otis King will last almost indefinitely and has no delicate parts which could be damaged easily.
the Otis King is a cylindrical slide rule
Because the scales are in spiral form they are much longer than would be practical in a flat rule. In fact although the Otis King scale occupies a space of only 2 inches it is really 66 inches long. It is, therefore, possible to mark many more graduations on the Otis King than on the flat type of slide rule which is normally no more than 10 inches in length. Slide rule users and those who have never used a slide rule before will appreciate the difference in accuracy from the following diagram showing a section of the Otis King scale and a section of the scale on a 10 inch slide rule.
The Otis King is durable and long lasting
Unlike many slide rules the Otis King is constructed principally of metal - there is no danger, therefore, of inaccuracies arising because of warping, shrinking or other damage affecting the scales. In addition the scales are printed on specially selected paper laminated with a plastic film to protect them from wear.
The Otis King is easily read
All exposed metal parts are heavily chromium plated except the cursor which is dead black. The contrast in colour facilitates the reading of the scales and obviates eye strain.
The Otis King is designed to do the job for which you buy it
It is always a sound policy to obtain a slide rule which has only the scales the purchaser will actually require. Many slide rules have a variety of different scales which are seldom used and often serve only to confuse. Such scales are not included on the Otis King, thereby enhancing its simplicity. Indeed by making available two different models, of equal accuracy, the Otis King covers the range of all work normally undertaken by a slide rule.

The two models available are:-
MODEL K For all Calculations involving multiplication, division and proportion, including costs, percentages and foreign exchange problems. Except where reading of logarithms is desired, it is recommended in preference to Model L, as the double scale on the cylinder frequently reduces the number of settings in a series of calculations.
MODEL L For all calculations for which Model K can be used. It gives in addition, logarithms of all numbers, by means of which roots and powers may be calculated.

What is the cost of 132
articles at 15/- per dozen ?
The diagrams on the opposite page give an example of how simple the Otis King is to operate.
Set bottom arrow on Cursor
to 15 on bottom scale.
The calculator comprises three metal tubes. Two of the tubes have spiral scales upon them with the smaller (called the Cylinder) being free to rotate and slide within the larger one (the Holder). The third tube is mounted on the Holder and forms a tubular Cursor, carrying at each end an engraved pointer which can be set to any mark on the scales or to which any mark can be set.
Set 12 on top scale to top arrow
of Cursor. The instrument is now
set to 15/- per dozen. The cost
of any number of articles at this
price can be obtained by moving
top arrow to number required,
as shown in 3rd movement
The operation of the Otis King is based on three simple movements (see opposite) and these form the basis of every calculation. The simplicity of the process is such that the calculator becomes even more invaluable as the number of factors involved in the calculation increase. Full working instructions, showing many applications of the simple three step principle, are supplied with every calculator and a few minutes study of these instructions will enable anyone to manipulate the calculator with accuracy.
Move top arrow to 132 on
top scale, and read answer.
165/- at bottom arrow

The following examples give a rough guide to the scope of the Otis King. Shown against each answer is the time taken to obtain it on the Otis King Calculator. The larger the number of terms in any given calculation the greater is the advantage in terms of time saved through using the calculator.
A What percentage of 37.392 is 4.53?
Answer = 12.12% (20 seconds).
B 74.5 × .027 × 38.93
.0041 × 962.1
Answer = 19.86 (50 seconds).
C 5738.5 kilos raw material produce 36,432 manufactured articles. How many ozs. does each contain?
(1 kilo = 2.2 lbs.). Answer = 5.542 ozs. (50 seconds).
D 363 Answer = 3.98 (1m. 40 seconds).
E 1.0083.1 Answer = 1.025 (1m. 40 seconds).
F 1.0083.1 × 363 × 4.000
6 × 5260000 × 421.82
Answer = .2495 (10 minutes).
G 3.75:4.71:12.25:x. Answer = 15.4 (25 seconds).
H What is the interest on $675.50 for 292 days at 3¾%?
Answer = $20.25 (20 seconds).
I What is the percentage of profit on cost where goods purchased for $5760 are sold for $9420?
Answer = 63.5% (15 seconds).
J Divide $760.525 in the proportions 400 : 680 : 75 : 36.
Answer = $255.37½ : $434.25 : $47.90 : $23.00. (90 seconds).
K What is the cost in shillings per cwt. of material offered at 45 cents per kilo? (£ = $2.80 ; 1 kilo = 2.2046 lbs.). Answer = 163.3/- (45 seconds).
L Convert 1750 Swiss francs into Rands.
(R1.00 = Sw. Frs. 6.14).   Answer = R285.00. (15 seconds).
M If I buy R1500 of 3½% stock at 103 3-16 what is the amount of the purchase and what rate of interest will it yield?
Answer = R1548. (15 seconds). 3.39% (15 seconds).

The OTIS KING is especially useful for metric calculations and for decimal currencies.

some of larger users of
Users of Otis King Calculators include many firms and institutions whose names are very well known. Many of the following have purchased not one, but several instruments, and have placed repeat orders from time to time, thus confirming their confidence in this popular calculating instrument.
Albright & Wilson Ltd. Imperial Chemical Industries Ltd.
Alginate Industries Ltd.Laporte Chemicals Ltd.
A.E.I.-Hotpoint Ltd.Lever Bros., Ltd.
Beecham Foods Ltd.Donald Macpherson & Co., Ltd.
Bowaters Trading Co., Ltd.Marchon Products Ltd.
British Oxygen Co., Ltd.Mullard Ltd.
W. & J Bush Ltd.John Mowlem & Co., Ltd.
Boots Pure Drug Co., Ltd.National Coal Board
Carpet Trades Ltd.Nestlé Co., Ltd.
Cheseborough-Ponds Ltd.Pfizer Ltd.
Carborundum Co., Ltd.Philips Electrical Ltd.
Distillers Co., Ltd.Rowntree & Co., Ltd.
Dunlop Rubber Co., Ltd.Spillers Ltd.
Electrical & Musical Industries Ltd.Turners Asbestos Cement Co., Ltd.
English Electric Co., Ltd.Unilever Ltd.
Samuel Fox & Co., Ltd.United Kingdom Atomic Energy
Fisons Ltd.Research Establishment
Gevaert Ltd.United Dominion. Trust Ltd.
Glaxo Laboratories Ltd.Yardley Ltd.

trades and professions using
There can be few industries and professions in which the Otis King would not be found useful: some of those in which it is already used are given below:
Accountants Motor Car Manufacturers
Agricultural CollegesMunicipal Departments
AnalystsOxygen Manufacturers
Atomic Energy EstablishmentsPhosphate Producers
BrewersPlastics Manufacturers
Cement ManufacturersPaper Mills
Co-operative SocietiesPaint Manufacturers
Copper WorksPetroleum Companies
Confectionery ManufacturersPottery Manufacturers
Chemical ManufacturersPoultry Farms
CollieriesRadio Valve Manufacturers
Civil Engineering ContractorsRailway Engineers
DistillersResearch institutes:
Electricity Supply Undertakings Agricultural, Industrial, Medical
Fertiliser ManufacturersRubber Manufacturers
Food Products ManufacturersStockbrokers
Government DepartmentsSmelters
Gas UndertakingsSoap Manufacturers
Hospital LaboratoriesShips' Engine Builders
Iron FoundersSteel Manufacturers
Iron & Steel ManufacturersTextile Manufacturers
Insurance CompaniesTelephone Cable Manufacturers
Income Tax ConsultantsTimber Merchants
Linen ManufacturersTimber Kiln Driers
Linoleum ManufacturersWoollen Goods Manufacturers
Match Manufacturers

what users think of

"I like your Calculator very much and could hardly be without one."
-Section Chief U.S. Bureau of Mines, Virginia.

"I am a Scientist and have found it of such great help that I have become accustomed to use it for quite trivial things in my daily life."
-Ph.D., Tangier.

"I have been using your Otis King Calculator for years and must have done aver 50,000 calculations with it; it has saved me hundreds of hours' hard work."
-Midsomer Norton.

"I use the Otis King Calculator for all my slide-rule work, and need the extra digit which normal slide-rules cannot give. I had to get one of my customers an Otis King last month, after using mine in his office."
-Textile Manufacturer.

"It does all you claim - 4 or 5 figure accuracy quite easily without eyestrain or the use of magnifiers - the logarithm scale gives the same degree of accuracy as normal 4-figure logarithm tables. Half-an-hour's study is ample for its use."
-Science Master.

This Otis King brochure is HTML'ized by Andries de Man from a copy provided by Dick Lyon from an original courtesy of Mr. Monroe Postman.