Photovoltaic cells were invented in the 1940s, and Patek Philippe produced a novel clock that used them. Once integrated circuit technology improved enough to build a quartz watch, American inventor Roger Riehl created the first solar-powered watch. His Synchronar paved the way for the solar digital watches that brought the technology to the masses in the 1970s. Then there was Uranus, with their wild calculator watch!
Some grails are special because of their association with history (see my piece on the “Scuderia Ferrari” Zenith, for example), while others are just plain odd. This is the latter. The Girard Perregaux Casquette (Ref. 9931) is a mid-1970’s LED quartz watch with innovations throughout. It’s just too bad the quartz revolution ended with a whimper instead of this kind of excitement!