And who can guess how it works? Paul O’Neil (editor-in-chief of WorldTempus)

How to read a BONHOFF
The time is read by turning the bezel in order to align the circles. The large circles represent the minute and the small circles represent the hour.

Reading the minutes
The minutes are read by turning the bezel in order to have the large circles match: ten minutes past
Reading the hour
The hour is read by turning the bezel in order to have the small circles match: ten o’clock
About reading accuracy
The considerable size of the large circles and the small distance between them allows the current minute to be readily identified with an accuracy of plus minus one minute. With the knowledge of the current minute, there are only twelve possible positions for the current hour. This lower required accuracy for the hour facilitates the smaller size of the hour circles the same way as a conventional minute hand allows the corresponding hour hand to be shorter.
About reading speed
The rotational friction of the bezel with its tactile “Clous de Paris” pattern is perfectly balanced to allow a fast and effortless yet smooth rotation of the discs. By starting the reading of the time with the minute it is an easy task to read the corresponding hour due to the fact that there only remain twelve possible positions for it. After a short phase of becoming familiar with the display system the reading of the time only takes a few seconds  –  a few seconds well spent with a fine watch.