GTM-06 a Tourbillon Minute Repeater with a Difference

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GTM-06
A tourbillon minute repeater with a difference

The GTM-06 minute repeater differs from other repeater wristwatches in a number of details. There is an acoustic reason for the large case design (44mm x 15mm) as the generous case volume allows the gongs to develop a full and pure sound.

The lugs, which also convey the full outlines of the case to the special galuchat strap, appear to be straightforward but they are not. Using specially developed micro-machining techniques invisible from the exterior, the lugs are specially channelled in order to allow the resonance of the case not to be dampened by their mass.

This is the result of much research and development as well as the vast wealth of experience that both Bart and Tim Grönefeld developed in the course of years of developing and listening to minute repeater mechanisms.

The dial is the top of the superbly finished movement – the calibre G-01 (see below for more details about the movement) – and the modern styled chapter ring of black onyx is adorned with highly polished hour indexes that catch the light at every angle to provide a subtle and discreet view of the time.

The GTM-06 fetaures the calibre G-01 and utilises a cathedral gong that circles the inside of the case twice, providing the fullest possible tone achievable. The majority of minute repeaters have a shorter gong making just one circumference of the case.

The movement is decorated with Geneva stripes, perlage, anglage and perfectly polished screws, hands, indexes and springs. Mirror black polish, the highly demanding fine finishing found only in the most exclusive watches, is used extensively throughout the movement.

Even those areas never seen by the user are given exquisite finishing on a level that has become increasingly rare in the world of haute horlogerie today.All in all, it takes more than two months of intensive work in several stages just to complete the fine finishing of the components before assembly even begins.

The GTM-06 is available in two limited editions of 10 pieces each: in 4N pink gold and in platinum

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Technical Specifications for the GTM-06

The GTM-06 is available in two limited editions of 10 pieces each: in 4N pink gold and in platinum

Case and dial

Material: 4N pink gold or 950 platinum

Lugs:Special channeled lugs to improve the sound of the minute repeater

Dimensions: 44mm x 15mm

Water resistance:2atm/20m/60feet

Dial: Open hour-minutes chapter ring made of natural black onyx

Hands:Hour and minute in pink gold or white gold with black nickel plating

Strap and buckle:Hand-sewn mat black, alligator leather with pink or white gold triple folding buckle

Movement

Calibre G-01:Mechanical, hand-wound movement; one-minute tourbillon, minute repeater

Number of components:385

Number of jewels:41

Power reserve:48 hours

Balance wheel:Glucydur with timing screws, 11 mm diameter

Frequency:18'000 vph/2.5 Hz

Balance spring:Breguet overcoil

Tourbillon:One minute Tourbillon, weight of cage 0.420 grams

Repeater:Classical mechanism visible through display back, cathedral gongs

Biography: Bart and Tim Grönefeld

The name Grönefeld and the art of watchmaking have a family history spanning a hundred years, originating in the ancient town of Oldenzaal in the Netherlands. There, in a shop facing the ancient basilica church from 1240, Johan Grönefeld, Bart and Tim’s grandfather, began his career as a watchmaker in 1912, marking the beginning of the highly talented dynasty of Grönefeld watchmakers that continues today.

Bart and Tim’s workshop is located in Johan Grönefeld’s original building, representing a continuous, unbroken watchmaking family history that is exceptionally rare to find anywhere in the world today.

Bart and Tim underwent extensive training in Switzerland, and within a relatively short span of time proved themselves adept world specialists in the production of the most coveted and exquisite horological complications of all: the tourbillon and the minute repeater wristwatch. In 2008, after working anonymously behind the scenes for prestigious Swiss brands, they presented the first watch bearing their own name, the GTM-06 Tourbillon Minute Repeater.

In 2010, Bart and Tim presented their second watch, the One Hertz, the world’s first series wristwatch with independent dead seconds and featuring a completely new movement, the G-02 Calibre. The One Hertz classic collection has grown to include the One Hertz 1912, One Hertz Dune, One Hertz Ruthenium, One Hertz Titanium and One Hertz Platinum, while the Contemporary collection, launched in 2012, includes the One Hertz Fire and the One Hertz Ice. In 2013, the open-dial One Hertz Techniek was launched.

The One Hertz is a prize-winning timepiece. It was awarded the Innovation prize in the 0024 WatchWorld Watch of the Year contest in 2011 and was voted Watch of the Year in 2011 by members of the influential watch forum Timezone.