Citizen Holdings Co., Ltd. is the core company of a Japanese global corporate group based in Tokyo, Japan. The company was originally founded as Shokosha Watch Research Institute in 1918 and is currently known as the manufacturer of CINCOM precision lathe machine tools as well as CITIZEN watches. The trade name originated from a pocket watch CITIZEN sold in 1924. It is one of the world's largest producers of watches. Eco-Drive watches use a battery recharged by a solar panel hidden under the watch face. In the rare and discontinued Eco-Drive Duo series, the solar power was supplemented by an automatic quartz power source. There was also an Eco-Drive Thermo model that exploited temperature differentials between the wearer's skin temperature and ambient temperature to recharge the battery. However, the only Eco-Drive system currently described on the Citizen Watch Official Web Site is the one depending solely on light to recharge. The Eco-Drive feature is similar to the Tough Solar battery charging system used in G-Shock watches by Casio. All Citizen Eco-Drive models are made in Japan but may also be assembled in China.