Sunday, May 7, 2017

Moritz Grossmann ATUM Date

Moritz Grossmann expands its ATUM family of classic mechanical watches by introducing a new model, the ATUM Date.

The date indication, a complication coveted and often discussed by watch enthusiasts, is a comparatively recent development in the long history of precision watchmaking. The first wristwatches with an analogue date were only just introduced in the early 20th century. For their date display in the ATUM Date, Grossmann's watchmakers adopted this classic format as well. A full date scale and an unusually shaped bracket marker emphasise the elegance and functionality of the model family. The jumping date combines a precisely legible display with mechanical ingenuity and a rare degree of convenience.
The calibre 100.3 of the ATUM Date is based on the calibre 100.1 of the ATUM line. Its characteristic elements, such as the pillar movement with 2/3 plate, wheel train, stop-work, removable winder module, escapement and oscillation system also feature the High-Artistic Finish. The jumping date mechanism is a complex ensemble of parts that are integrated in the main plate on the dial side. Both the winder and the hand-setting mechanism are taken from the calibre 100.1. To prevent a simultaneous reverse adjustment of both systems or damage to the date switcher, the separate date setting mechanism is uncoupled with a stop lever as soon as the hand-setting crown is pulled and the stop seconds device stops the watch.
The jumping date relies on a complex system composed of the date switching ratchet, release lever, switching star, and the date ring with the bracket-style marker. The date ratchet consists of the wheel itself, a ring-shaped switching finger spring, and the switching finger. The switching finger can freely rotate on the wheel but is secured by the ring spring in a position that allows movements on both sides but always requires tensioning of the spring. The mechanism is powered by the hour wheel at a ratio of 2:1, so the ratchet wheel fully rotates anticlockwise once every 24 hours. The transmission ratio of the date marker mechanism is calibrated to 11.6°, so the increments of the date ring add up to a total of 31 days.
Apart from the precisely jumping date, this type of date display has the advantage that the switching finger does not engage with the wheel train except for the few milliseconds during which the jump to the next date is taking place. The date can be changed in either direction at any time while the movement continues to run. The separate setting crown at 10 o'clock allows the date to be easily corrected, for instance at the end of a month. Normally, this setting crown is not engaged, so inadvertent adjustments are prevented. The crown must be pulled out to set the date. During the process, the movement continues to run and the date can be set by turning the crown in either direction. A jumper spring causes the date ring with the marker to precisely engage in the selected position.

On the solid-silver dial, the minute scale is shifted inward to provide space for the complete date scale from 1 to 31. The blue date numerals clearly contrast against the applied hour markers. To avoid competition with the hour and minute hands, the date indicator points to the date from the circumference instead of from the centre. Lavishly finished by hand, the bracket-shaped date marker is annealed to a brown-violet hue to contrast against the blue date numerals. The ATUM Date is fitted with the typical lancet-style hands. In the manufacture, they are crafted, finished, and annealed to a brown hue to match the rose-gold case. For the white-gold model, all hands are made of polished stainless steel. 

With the complete date scale in both versions, the ATUM Date delivers an impressive sense of the progression of days.  The ATUM Date is presented in rose-gold and white-gold versions.

Technical details

Movement   
Manufacture calibre 100.3, manually wound, adjusted in five positions
No. of parts: 259
No. of jewels: 26, of which 3 in screwed gold chatons
Escapement: Lever escapement
Oscillator: Shock-resistant Grossmann balance with 4 inertia and 2 poising screws, Nivarox 1 balance spring with No. 80 Breguet terminal curve, Gerstenberger geometry
Balance: Diameter 14.2 mm, frequency 18,000 semi-oscillations per hour
Power reserve: 42 hours when fully wound
Special features: Grossmann balance; hand-setting override and start of movement with lateral pusher; precisely jumping date display with a peripheral marker; bidirectional date adjustment with a separate crown at 10 o'clock; space-saving modified Glashütte stopwork with backlash; adjustment with Grossmann micrometer screw on cantilevered balance cock; pillar movement with 2/3 plate and pillars made of untreated German silver; balance cock and escape-wheel cock hand-engraved; broad horizontal Glashütte ribbing; 3-band snailing on the ratchet wheel; raised gold chatons with pan-head screws; separately removable clutch winding mechanism; stop seconds for handsetting
Movement dimensions: Diameter: 36.4 mm, height: 7.56 mm

Functions    
Hours and minutes, subsidiary seconds with stop seconds, date display, Grossmann manual winder with pusher

Operating elements   
Two crowns in 750/000 gold to wind the watch and set the time and the date, pusher in 750/000 gold to start the watch

Case   
Three-part, precious metal
Diameter: 41.0 mm, height: 11.85 mm
Crystal and display back: Sapphire crystal, antireflective coating on one side

Dial   
Solid silver, hour markers in gold
Hands: Manually crafted, in steel or stainless steel

Strap    
Hand-stitched alligator strap with prong buckle in precious metal

Versions
Reference: MG-000804
Case: 750/000 rose gold
Dial: Argenté
Hands: Manually crafted, steel annealed to a brown hue

Reference: MG-000807
Case: 750/000 white gold
Dial: Argenté
Hands: Manually crafted, polished stainless steel

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