The Clamshell's 15-year history began in 1936 when Gallet purchased the rights to a patent for the "waterproof" watch case design (Brevet N° 189190), invented by the Swiss firm of Schmitz Frères & Cie in the neighboring city of Grenchen.
The "waterproof" Clamshell filled such a critical void in the area of military, industrial, and sports related timekeeping that its popularity helped Gallet's overall sales of wrist-worn watches and hand-held timers exceed 100,000 units per year for over 15 years.