In reply to Roger Sweeting.

Hi Roger,
It sounds like you may have a slide rule bezel, rather than a standard timing bezel or GMT bezel. There are many different types of bezels, and the type of scale(s) printed on them can dictate both how they function and what can be done with them. A slide rule bezel features a logarithmic scale that can be used to perform a number of different calculations. You will often see slide rule bezels on pilot's watches since they can be used to help multiply and divide values and convert units of measurement, functioning in a similar manner to an analog flight computer.
The Breitling Navitimer is one of the most famous watches to feature a slide rule bezel. Check out this article of ours for more info - it uses a Navitimer as the example, but the same principles will work for any watch with a slide rule bezel.