The Piaget Altiplano Ultimate Concept, presented at SIHH in 2018, was at launch the thinnest mechanical watch in the world, at 2 mm tall. It has a 41 mm case made of a cobalt alloy that doubles as the movement baseplate, and it is powered by the hand-wound calibre 900P-UC, which is only 2 mm thick overall. Sapphire crystal covers the dial.

The watch comes from Piaget’s long history of ultra-thin movements, going back to the 9P calibre of 1957. The case and the movement were merged into a single structure, which removed the usual separation between the two and allowed the extreme thinness, with a 43-hour power reserve reported by Piaget.

The Ultimate Concept was praised as a technical achievement, although its thinness meant some compromises in everyday use, as with all very thin watches. Its record was later overtaken by other ultra-thin models. Piaget continues to offer versions of the Altiplano Ultimate Concept, so the production status is left blank.