This ingenious sundial in pocket size is the modern version of a historic model that can be found at the Royal Observatory in London, Greenwich. It is manufactured in Austria by H.M.Kala, a family of Austrian watchmakers. The sundial is just 6 cm in diameter and therefore meets the international sizing standard for pocket watches. It weighs 40 grams.
The sundial’s main body is made of brass with the small selector in the middle being stainless steel and the outside ring being steel. The brass and the steel parts are sourced from Germany. The numbers, letters and other marks on the sundial are colored unevenly in black to give the sundial an ancient look.
The pocket sundial is able to tell the true solar time everywhere in the world at any point in time (as long as the sun is shining), as it can be adjusted for geographical latitude and time of the year. Its average accuracy is estimated to be better than +/- 10−15 minutes relative to the true solar time.
When set up for reading the time, the sundial is a small model of our planet with the middle bridge being parallel to the earth’s axis, the inner ring being parallel to the equator and the outer ring being positioned in a north-south direction. In this way, the sundial can also serve as a compass. For easy transport, the inner and outer rings can be folded together.
The pocket sundial should be stored in a dry place and kept away from leather, as the substances used in tanning leather can interact with the brass alloy.