I was given a very cool present this Christmas period by my in laws (Check out Rachel’s fitness blog here and also this pretty incredible photo of Bryn in Antartica here). It’s an old school Otis King calulator which based on wikipedia was made sometime between 1922 and 1972.

Here it is in it’s box:

The box contains some (pretty old looking) instructions and the calculator itself:

This calculator allows you to carry out multiplication and division pretty easily thanks to the use of a logarithmic scale.

This video is a pretty good demonstration of how to work it:

If you don’t have time to look at that short video here’s the basics of trying to multiply 14 by 6. The calculator is made up of two cylinders seperated by a slider with two markers:

First we put the bottom marker on 14:

Once we have done that we align the top marker with a ‘ONE’ (there are three of them) at the top or bottom (of the upper cylinder). We do this by keeping the bottom marker aligned on the 14:

The final step is to move the top marker to 6 and read the result of the product on the bottom marker:

As can be shown in the photo the result is 84.

As you can see in the video (and or might be able to work out) it’s pretty simple to invert this process to carry out division also. For example the following photo shows the last step of 84/5= 16.8.

This is such a neat little calculator and a very cool gift. Not quite sure I’ll be letting go of my smart phone just yet but this will go really nicely on the desk in my office.