After much deliberation I bought a Sinn 556I. As a pilot I wanted a watch that would be easily legible, luminous and tough enough to withstand significant changes in temperature, pressure and humidity. A high quality automatic movement ensures that my watch will not stop from lack of winding or a flat battery - another important aspect in ensuring consistent time-keeping. The Sinn is undoubtedly the most clear and easily read watch I have owned, the bright white hands and markings standing out strongly against a dark and glossy black face. In my view this is the optimum configuration for legibility. Every part of the watch exudes quality making the watch feel bullet-proof while at the same time the slightly smaller than 40mm diameter results in a feeling of wearability and unobtrusiveness thus allowing the watch to be worn for any purpose.