The index adjuster
The calibre 201.0/201.1 of the ATUM Pure is a pillar movement consisting of the main plate and the typical 2/3 plate. A glance through the display back reveals the unusual appeal of Grossmann’s Pure Classic Finish. Specially developed for the steel case of the ATUM Pure, the calibre showcases purity in materials and straightforward execution.
The untreated German silver plates are shot-peened with glass beads. This technique matts the surface and makes it sensitive, so great care is called for in the assembly process. Rather than with decorative chatons, the white sapphire bearing jewels are pressed directly into the plate and sparkle thanks to their chamfered seats. Flat polished movement screws with the original sheen of steel accentuate the monochrome allure. The focus is on the multicoloured oscillation system.
The calibre 201.0/201.1 movement directs the observer’s attention straight to technical details. In the oscillation system, the Grossmann balance is paired with a hand-bent flat hairspring. To fine-tune the frequency of the oscillator, the inertia screws in the balance wheel rim can be exchanged crosswise with screws from one of the five different mass categories.
Instead of forming the adjuster curve of the flat balance spring using a fixture, the material is carefully bent out by hand to keep the curb pin free. The outer attachment point is specially modified for the flat hairspring. It receives a double bend before being pinned to the stud. This bend allows the adjuster curve to be accurately centred.
The index adjuster
The calibre 201.0/201.1 provides convenient options for adjusting the oscillation system; they are superior in design to conventional solutions.
The beat and rate can be adjusted separately with a micrometer screw and without removing the oscillation system. For this purpose, the cantilevered balance cock is fitted with a rotatable stud holder. In the calibre 201.0, the bearing and thus the guide element of the stud holder were elaborately optimised. The beat of the oscillator can be adjusted by moving the index tail. By tightening a clamping plate, the stud holder can be easily immobilized so that moving the index tail now adjusts the rate of the oscillator.
There is absolutely no play between the index adjuster, the stud holder, and the upper balance bearing. This allows the ATUM Pure to be precisely adjusted at all times.
Manufacture calibre 201.0/201.1, manually wound, adjusted in five positions
Grossmann balance; handsetting override and start of movement with lateral pusher; space-saving modified Glashütte stopwork with backlash; adjustment with Grossmann micrometer screw on a cantilevered balance cock; pillar movement with 2/3 plate and frame pillars in untreated German silver; separately removable clutch winding mechanism; stop seconds for handsetting
Hours and minutes, subsidiary seconds with stop seconds, Grossmann winder with pusher
No. of parts
No. of jewels
Shock-resistant Grossmann balance with 4 inertia and 2 poising screws, Nivarox 1 balance spring
Diameter 14.2 mm, frequency 18,000 semi-oscillations per hour
42 hours when fully wound
Crown for winding the watch and setting the time, pusher to start movement
Diameter: 36.4 mm, height: 5.0 mm