Bit of History:
Calibre 21 movement is an ultra-thin hand-wound by Swiss watchmaker Frederic Piguet. It was the worlds thinnest watch movement made from 1925 through the 2000's and remained holding the record for 21 years and sold to many other manufacturers like Patek Philippe Cal. 175 and 177, Blancpain 21, Movado, Bueche-Girod, Corum, Gubelin, Girard-Perregaux and etc.