Mondaine Digi-Solar

European Watch Clock and Jewellery Fair 1977 EF 327
A solar-cell solid-state watch of entirely new design. The cells and battery were developed in tandem for greater operational efficiency. The cells themselves react to intense light only but 4 minutes’ exposure is enough to recharge the 60 Ah battery for one month. It requires a battery change only every 3 to 5 years. Its 6-digit alphanumeric display, designed specially by Brown Boven, features a calendar programmed to the year 2100. 12-hour or 24-hour cycle, selected simply by turning a screw. With nightlight. (MONDAINE Digi-Solar)