Jean Lassale was founded in 1976 and specialized in ultra-thin watches. The company produced both quartz and mechanical watches, casing a 1.2 mm mechanical movement in a 3 mm case. These movements and patents were purchased by Claude Burkhalter, who founded Nouvelle Lemania in 1982. The resulting movements were licensed to Piaget, who has continued this tradition.
Lassale also produced high-end cases for Seiko, which fitted them with their quartz movements for their Credor line. This cooperation lasted from 1977 through 1979, when the company gradually became a Seiko subsidiary. By 1981 Seiko was producing co-branded Seiko Lassale watches, with later products branded Jean Lassale or just Lassale. Seiko produced their Seiko Lassale products entirely in Japan, though the design was similar to previous Swiss products. One special model from 1981 was a Seiko Lassale Centennial, commemorating the company's 100th anniversary and etched with Kentaro Hattori's signature.
In 1991, Seiko re-launched Lassale as a high-end brand intended to compete with the elite Swiss manufacturers. These products featured solid gold cases, diamonds, and other luxury touches. But lower-end movements were substituted for the early specialty calibres. Seiko cancelled the Lassale brand in the 2000's.
Lassale is best known for their Calibre 1200, the thinnest in the world at that time. This technology went to Nouvelle Lemania in 1982, a few years after the company went bankrupt and the name was sold to Seiko.
Calibre 1200 was introduced at the Basil Fair in 1976. It was 20.4 mm in diameter, 1.2 mm thick and used 14 0.2 mm ball bearings, a novel design. It ran at 21,600 A/h, had 11 jewels, and a power reserve of 35 hours.
Calibre 2000 was an automatic variant of Calibre 1200. It was 2.08 mm thick.
Both calibres 1200 and 2000 were produced from 1976 through 1979 in Geneva. Nouvelle Lemania produced successor movements to these, the 1210 and 2010, respectively, in the 1980's. These were used by Piaget until their acquisition by Cartier. After this, Vacheron Constantin also used them.
Seiko produced special versions of their 7A series analog quartz chronograph movements for Lassale wrist and pocket watches, Calibres 7A54 and 7A75, which were more decorated but otherwise similar to the standard movements.