PATINA 7

This oversized chronograph was made between 1933 and 1952, however despite almost two decades of production, only 14,000 movements were manufactured. It was a development of the significantly smaller 28.9 chronograph and the increased size gave the watch far superior accuracy and reliability. It also allowed a far more detailed dial which meant a variety of scales could be used whilst remaining easily legible. These watches were not fashionable at the time and would have been exclusively purchased by individuals who had needed to use the watches for calculations, such as speed measurements. This example has a triple Tachymeter scale that can measure speed from 1000km/h to 12km/h over 3 minutes as well as a Telemeter scale for measuring distance using sound.

The Patina:

It is believed that the extensive patina on the dial is caused by the gradual ingression of moisture in the case, coupled with exposure to ultra-violet light from prolonged periods in the sun. The UV exposure can cause degradation in the paint which had no UV protection at the time. This degradation can cause the dial to discolour and the lacquer around the paint to craze. This causes fissures in the coating which allows moisture to penetrate to the base metal resulting in speckles of oxidisation which is more concentrated where the paint is present.