Ultra thin watchmaking is the collision point between possibility and impossibility. It poses challenges so particular to the genre where the traditional goals of watchmaking — reliability, durability and chronometric performance — are forced into conflict with the pursuit of thinness itself. What remains is a discipline defined by the ingenuity of the solutions that make such watches possible at all. Thus, while records in ultra thin watchmaking are increasingly short-lived today, the solutions are the things remembered. The 2.0mm-thin Piaget Altiplano Ultimate Concept (AUC) Tourbillon, created for Piaget’s 150th anniversary in 2024, was a gripping achievement as many of its solutions drew a line between what has become conventional practices in ultra thin watchmaking and far more radical departures.

The 2.0mm-thin Piaget Altiplano Ultimate Concept (AUC) Tourbillon (©Revolution)

The mainspring barrel is one of the latter, and it has been largely overlooked. It goes beyond the familiar suspended or “hanging” barrel, supported only at its base and dispensing with the upper bridge. The ratchet wheel itself encloses the mainspring without the need for a barrel cover. The barrel is no longer a closed drum but reduced to a cylindrical wall with peripheral teeth, lacking both base and cover.

It sits openly on the baseplate itself, which serves as its floor. The barrel arbor and ratchet wheel are made as a single piece, and this entire part pivots on a fixed shaft that rises from the base plate. With nothing to stabilize it, such a wall cannot rely on conventional jewel pivots. In other record-breaking watches, rollers placed around the drum provide guidance, but at the cost of enlarging the footprint. In the Altiplano Ultimate Concept Tourbillon, space is scarce in every dimension: not only vertical but also lateral, since the movement must house a tourbillon while remaining within a classical round case of wearable proportions. Thus, Piaget turned to a ball bearing. A groove in the inner wall of the barrel faces acor responding groove in an outer fixed ring, the two forming an annular track in which the balls run. The result is a compact bearing that lets the barrel turn with minimal friction, without adding to its diameter.

Details on the dial (©Revolution)

The second radical departure, and the heart of the watch, is the flying tourbillon itself, which has been flattened into the plane of the movement. This is astonishing when you consider that a traditional tourbillon consists of about six layers — the balance wheel, escapement, escapement bridges, escape wheel pinion, which meshes with the fixed fourth wheel, upper cage bridge and lower cage bridge — or seven layers if you include the cage pinion. In the AUC, the upper and lower cage bridges are realized as two titanium plates, clamping between them the balance, balance spring, staff and escapement. Screwed to the lower plate is a spokeless toothed wheel that serves both as the escape wheel bridge and as the driving element for the cage itself.

The flying tourbillon (©Revolution)

The escape wheel meshes with a fixed wheel with internal teeth, while the spokeless wheel is driven at its periphery by the last gear of the going train. The entire tourbillon module does not turn on pivots but is carried at its rim in a ceramic ball bearing, with the balls running between an inner race machined into the upper bridge and an outer race fixed in the frame. Eventhebalancestaff dispenses with opposed pivots and jewels, turning instead in a separate ball bearing embedded directly into the bridge.

Details on the dial (©Revolution)

By supporting the cage at its circumference, the design allows the balance to be offset from the central axis, avoiding overlap with the escape wheel pinion and keeping the overall thickness under control. Additionally, by folding functions into the plates themselves, further parts are eliminated. The stud holder for the hairspring is anchored directly into the titanium cage, which also carries the pallet fork, while the banking pins are cut straight into the rim. For these and other solutions, it remains an extraordinary accomplishment; more so given that such radical concessions to thinness have been brought to heel within the classical round form of a wristwatch.

Piaget Altiplano Ultimate Concept Tourbillon (©Revolution)

Tech Specs: Piaget Altiplano Ultimate Concept Tourbillon

Movement Manual winding Caliber 970P-UC; 40-hour power reserve
Functions Hours and minutes; one-minute peripheral flying tourbillon
Case 41.5mm × 2.0mm; M64BC cobalt alloy with blue PVD treatment; water resistant to 20m
Dial Monobloc design with off-centered time display
Strap Dark blue calfskin with 3D-printed maille polonaise mesh motif; M64BC cobalt alloy pin buckle