Last February I attended GTE 2102 and got introduced to the GANGI watch brand. On the other side of each of their watches there is an entire system which has been patented, that allows the timing of a chess game.
The best explanation you can get to understand the birth and the workings of the GANGI pocket watches, is to listen to the designer and owner, Mr. Pasquale Gangi himself:
video by montres24.com
The GANGI watch in its leather case that can be mounted to your belt.