THE OTIS KING  
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:  
THE OTIS KING IS  
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.  
WHY THE OTIS KING IS SO ACCURATE  
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. 
PROBLEMS SOLVED WITH SIMPLICITY 
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.  
 
THREE BASIC PARTS  
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.  
 
THREE BASIC MOVEMENTS  
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.  

SPEED AND SCOPE  
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  ^{3}√63 Answer = 3.98 (1m. 40 seconds).  
E  1.008^{3.1} Answer = 1.025 (1m. 40 seconds).  
F 
1.008^{3.1} × ^{3}√63 × 4.000
6 × ^{5}√260000 × 42^{1.82} 
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 ;
 
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 103 316 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  
THE OTIS KING CALCULATOR  
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.  
CheseboroughPonds 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  
OTIS KING CALCULATORS  
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 Colleges  Municipal Departments  
Analysts  Oxygen Manufacturers  
Atomic Energy Establishments  Phosphate Producers  
Brewers  Plastics Manufacturers  
Cement Manufacturers  Paper Mills  
Cooperative Societies  Paint Manufacturers  
Copper Works  Petroleum Companies  
Confectionery Manufacturers  Pottery Manufacturers  
Chemical Manufacturers  Poultry Farms  
Collieries  Radio Valve Manufacturers  
Civil Engineering Contractors  Railway Engineers  
Distillers  Research institutes:  
Electricity Supply Undertakings  Agricultural, Industrial, Medical  
Fertiliser Manufacturers  Rubber Manufacturers  
Food Products Manufacturers  Stockbrokers  
Government Departments  Smelters  
Gas Undertakings  Soap Manufacturers  
Hospital Laboratories  Ships' Engine Builders  
Iron Founders  Steel Manufacturers  
Iron & Steel Manufacturers  Textile Manufacturers  
Insurance Companies  Telephone Cable Manufacturers  
Income Tax Consultants  Timber Merchants  
Linen Manufacturers  Timber Kiln Driers  
Linoleum Manufacturers  Woollen Goods Manufacturers  
Match Manufacturers 
what users think of  
THE OTIS KING CALCULATOR  
"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 sliderule work, and need the extra digit which normal sliderules 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 4figure logarithm tables. Halfanhour's study is ample for its use."  
Science Master. 