Straightforward, authentic, artisanally perfect. The special features of the second TEFNUT calibre in detail:
As regards its architecture and technical details, the calibre 202.0 corresponds to the calibre 102.0. The dimensions – 26 mm in diameter and nearly 4 mm in height – are unchanged. With the salient 3/5 plate and the harmoniously arranged and proportioned components, the heart of the TEFNUT Pure is technically identical yet puristically reduced to the essence.
In the 19th century, Moritz Grossmann already realised that small pinions with six leaves produce very unfavourable transmission ratios. To avoid this phenomenon, he used a 16-tooth escape wheel. This concept was adopted for the escapement integrated in the calibre 202.0 movement. Due to the somewhat higher frequency of the smaller balance, it was fitted with an escape wheel that has 18 very slender, classically shaped teeth.
THE INDEX ADJUSTER
The Grossmann balance has four interchangeable inertia screws that can be used for a first-pass balance-spring matching process. Two precision poising screws make it possible
to fine-tune the frequency. The balance-wheel rim features 22 equidistant bores. For material removal purposes, they can be countersunk or broached to accurately true the balance without damaging the finished rim surface.
The index pointer enables the daily rate to be corrected without jeopard-ising the integrity of the balance. It is easily accessible once the caseback has been removed.
THE WHEEL TRAIN
Departing from the mainspring barrel, where according to Glashütte regleur Alfred Helwig the adjustment of a movement must begin, the wheel train of the calibre 202.0 reflects a new concept. The barrel is bilaterally supported in jewel bearings, which reduces friction, optimises the energy balance, and improves the rate accuracy of the watch.
Normally, the barrel engages with the wheel train directly at the centre wheel, located at a height that lies between the barrel and the ratchet wheel. To achieve a thinner silhouette and make the best possible use of the space in the round movement available to the wheel train, the centre wheel was shifted to a different position in the TEFNUT calibre. The power produced by the mainspring barrel is now transmitted to an intermediate wheel by a single pinion and from there passed on to the repositioned centre wheel.
A copper-nickel-zinc alloy called ARCAP assures the long-term brilliance of the wheels.