Sell

Index

Home

Learn

Service

About

Marketplace

Get the app

About Us

Buyer Protection

The Wristcheck Grade

Authenticity Guarantee

Wristcheck Watch Glossary

The Wristcheck App

Our Team

Careers

Book An Appointment

Watch Care & Service

Shipping, Returns and Warranty

How to Buy

Visit Us

Contact Us

<a href="https://wa.me/85223181777?text=Hi%2C%20I%E2%80%99m%20interested%20in%20buying%20or%20selling%20a%20watch." target="_blank" rel="noopener noreferrer">Want to buy or sell a watch? WhatsApp us</a>!

WCNEW100 for US$100 off orders over US$5,000

<a href="https://wa.me/85223181777?text=Hi%2C%20I'm%20interested%20in%20a%20specific%20watch.%20Can%20you%20source%20it%20for%20me%3F" target="_blank" rel="noopener noreferrer">Looking for a watch? WhatsApp us and we’ll source it!</a>

Own <a href="https://wristcheck.com/buy/sell-your-watch--a" target="_blank" rel="noopener noreferrer">these watches</a>? Consign to save 2% on fees. <a href="https://wa.me/85223181777?text=Hi%2C%20I'd%20like%20to%20sell%20my%20watch%20to%20save%202%25%20on%20seller%20fees.%20Can%20you%20help%3F" target="_blank" rel="noopener noreferrer">WhatsApp us for details</a>.

Looking to buy a watch? <a href="http://wristcheck.com/buy" target="_blank" rel="noopener noreferrer">Shop Now</a>

Interested in Rolex watches? <a href="http://wristcheck.com/buy/rolex" target="_blank" rel="noopener noreferrer">Shop now</a>

Interested in AP watches? <a href="http://wristcheck.com/buy/audemars-piguet" target="_blank" rel="noopener noreferrer">Shop now</a>

Interested in Patek watches? <a href="http://wristcheck.com/buy/patek-philippe" target="_blank" rel="noopener noreferrer">Shop now</a>

Interested in Cartier watches? <a href="http://wristcheck.com/buy/cartier" target="_blank" rel="noopener noreferrer">Shop now</a>

Interested in Omega watches? <a href="http://wristcheck.com/buy/omega" target="_blank" rel="noopener noreferrer">Shop now</a>

Interested in Tudor watches? <a href="http://wristcheck.com/buy/tudor" target="_blank" rel="noopener noreferrer">Shop now</a>

Interested in Bulgari watches? <a href="http://wristcheck.com/buy/bulgari" target="_blank" rel="noopener noreferrer">Shop now</a>

Not sure where to start? <a href="https://wa.me/85223181777?text=Hi%2C%20I%20would%20like%20to%20get%20a%20quote%20to%20sell%20my%20watch.%20Would%20you%20be%20able%20to%20help%3F" target="_blank" rel="noopener noreferrer">WhatsApp us</a> to get a quote!

WCNEW500 for US$500 off orders over US$20,000

WCNEW1000 for US$1,000 off orders over US$30,000

We accept alternative payment methods. Contact payments@wristcheck.com for details.

Looking for a watch? <a href="imessage://concierge@wristcheck.com&amp;body=Hi%20I%20want%20to%20learn%20more%20about%20Wristcheck." target="_blank" rel="noopener noreferrer">Message us</a> on iMessage

Banner_0.jpeg

All Categories

logo.png

All articles featuring Greubel Forsey watches

Greubel Forsey

The Best Independent Watchmakers Every Collector Needs To Know

12 Watches To Wear In The Year Of The Rabbit

Powered by an all new movement and a unique conical case, the latest iteration of the Tourbillon 24 Secondes is not just sleeker than its predecessors but also a testament to the brand’s unwavering quest for mechanical excellence and accuracy

&nbsp;

This April, as we were out and about in Switzerland, exploring the tiny watchmaking towns around Geneva, we drove up to La-Chaux-de-Fonds — a UNESCO World Heritage site recognised as one of the world’s most important watchmaking centers. Home to over 100 companies – both big and small – this is where more than half of the world’s watches were being made until the beginning of the 20th century.&nbsp;

Our first stop in this ‘watch valley’ was Greubel Forsey. Nestled atop a grassy hillock, Greubel Forsey’s ultra modern atelier is hard to miss. The tall, triangular, all-glass facade is actually a 17th century farmhouse that was purchased by the company’s founders in 2007. Emblematic of Greubel Forsey’s watchmaking philosophy – merging traditional crafts with groundbreaking technologies – the facility offers a fascinating peek into the future of haute horology from Switzerland. And this is where we got the first glimpse of the new Tourbillon 24 Secondes Architecture, which in many ways, is emblematic of a new aesthetic direction for the brand.&nbsp;

&nbsp;
<img alt="GF" data-caption="Greubel Forsey’s ultra modern atelier in La-Chaux-de-Fonds is a 17th century farmhouse that was purchased by the company’s founders in 2007" data-entity-type="file" data-entity-uuid="374de11d-cf65-4852-bf04-0156c3f75842" data-image-style="blog_inline_image" height="1046" src="https://wc-strapi.s3.ap-east-1.amazonaws.com/article_import/images/141/Greubel-Forsey-Farm-and-Atelier-1600x900.jpeg" width="1568" /><img alt="GF" data-caption="Although the Tourbillon 24 Secondes Architecture measures 47.05mm in diameter, it feels absolutely light on the wrist, thanks to the use of Grade 5 titanium" data-entity-type="file" data-entity-uuid="76609b0a-3573-44e6-bab3-fe63e5bcbdc5" data-image-style="blog_inline_image" height="1046" src="https://wc-strapi.s3.ap-east-1.amazonaws.com/article_import/images/141/DSCF0510_0.jpg" width="1568" />
&nbsp;

The latest iteration of Greubel Forsey’s fastest rotating and inclined tourbillon, the 24 Secondes Architecture is part of the ‘Convexe Collection’ that focuses on lightweight titanium watches. While we have all been in awe of the brand’s hypnotic inclined escapements and multi-axis tourbillon cages, these sculptural timepieces – most of us would agree – aren’t easy to wear. Powered by an all new movement and a wrist-friendly conical case, the Tourbillon 24 Secondes Architecture is not just sleeker than the previous models but also a testament to the brand’s quest for mechanical excellence and accuracy.&nbsp;

Let’s deep dive and find out how Greubel Forsey managed to pack all its technical know-how in a unique architectural experience for the wrist.&nbsp;

&nbsp;

<h3>A Conical Case&nbsp;</h3>

To make this complicated watch much more wrist-friendly than its previous offerings, Greubel Forsey has moved over the traditional case construction to a conical frustum ( a hollow cone with its top sliced off) design that has enough room to accommodate the 354 components without making the watch look bulky. Interestingly, the diameter of the caseback (47.05mm) is slightly wider than the bezel (45.5mm) and this lends a compact feel to the overall aesthetics.&nbsp;

While the case looks perfectly round at first glance, the transparent sides reveal its convex shape from different angles. Thanks to the sapphire crystal ring around the caseband, one can truly admire the complex movement in all its glory from the front, back and even the sides.

&nbsp;
<img alt="GF" data-caption="While the case looks perfectly round at first glance, the transparent sides reveal its convex shape from different angles" data-entity-type="file" data-entity-uuid="e93e1a03-e05f-43c7-b768-da5227680464" data-image-style="blog_inline_image" height="1046" src="https://wc-strapi.s3.ap-east-1.amazonaws.com/article_import/images/141/DSCF0517_0.jpg" width="1568" />
<h3>&nbsp;</h3>

<h3>Bare-All Architecture&nbsp;</h3>

Living up to its name, the Tourbillon 24 Secondes Architecture pulls you into its deep, three dimensional face that has plenty of high points to study and admire. The watch dial actually bares open the hand-wound movement made of exceptionally finished components. While Greubel Forsey has been bestowing its complex dials with small sapphire windows since 2007, this is the first time, it has exposed the movement in its entirety, thanks to a transparent mid-case and the sapphire crystal on the caseback.&nbsp;

The most captivating aspect of this three-dimensional piece is the sight it offers from the aperture at 6 '0 clock on the caseband – it’s thrilling to see the 24-second tourbillon (that rotates once every 24 seconds on a 25° to ensure exceptional accuracy) &nbsp;inclination in action from this unusual angle!

Talking about the most obvious functions on the watch, the hours and minutes on this piece are indicated with the help of two large curved and openworked hands crafted out of polished steel. While the small second indication is displayed at &nbsp;8 o'clock, the power reserve indicator is discreetly placed at three o'clock and is supported by an individual titanium bridge. The watch gets its captivating depth from not just the inclined 24-second tourbillon but also from the three-dimensional curved grade 5 titanium bridges of the tourbillon, barrel and power reserve indicator.

&nbsp;
<img alt="GF" data-caption="The most captivating aspect of this three-dimensional piece is the sight it offers from the aperture at 6'0 clock on the caseband – the whirling 24 secondes tourbillon in action&amp;nbsp; Photo: Greubel Forsey" data-entity-type="file" data-entity-uuid="195c302e-4202-49c3-9772-f1879014471e" data-image-style="blog_inline_image" height="1046" src="https://wc-strapi.s3.ap-east-1.amazonaws.com/article_import/images/141/Greubel%2520Forsey%2520Tourbillon%252024%2520Secondes%2520Architecture_4595_006.jpeg" width="1568" />
<div class="hytPlayerWrapOuter">
<div class="hytPlayerWrap"><iframe frameborder="0" height="360" src="https://www.youtube.com/embed/ph7UYHJ6WTc?rel=0&amp;enablejsapi=1" width="640"></iframe></div>

<div class="hytPlayerWrap">&nbsp;</div>

<div class="hytPlayerWrap">&nbsp;</div>

&nbsp;
</div>

<h3>Exceptional Finishing&nbsp;</h3>

As always, Greubel Forsey has used the most exceptional finishing techniques on not just the watch’s exterior but on each and every geometrical component. Polishing grade 5 titanium is no easy feat but in this case, the brand has mirror polished even the arched bridges to perfection — enhancing the allure of super smooth, reflective surfaces. The caseback reveals some portion of the gear train on the large base plate frosted on top and mirror polished on its bevels. The lower bridge for the tourbillon is also concentrically brushed and beautifully hand beveled on the sides. &nbsp;

Greubel Forsey will be making only 11 of the 24 Secondes Architecture in 2022, followed by 18 pieces a year until 2025 for a total of 65 overall.&nbsp;

&nbsp;
<img alt="GF" data-caption="The caseback reveals some portion of the gear train on the large base plate frosted on top and mirror polished on its bevels" data-entity-type="file" data-entity-uuid="94b6a51f-58a7-401f-a448-3c6875811afb" data-image-style="blog_inline_image" height="1046" src="https://wc-strapi.s3.ap-east-1.amazonaws.com/article_import/images/141/DSCF0543_0.jpg" width="1568" /><img alt="GF" data-caption="It takes nearly a week to mirror polish the bridges of the barrel and the tourbillon" data-entity-type="file" data-entity-uuid="c9499e04-f3f9-4fa3-8274-b5be55d79a79" data-image-style="blog_inline_image" height="1046" src="https://wc-strapi.s3.ap-east-1.amazonaws.com/article_import/images/141/05-Grebuel-Forsey-Tourbillon-24-Secondes-Architecture.jpeg" width="1568" />
&nbsp;

<h3>Tech Specs</h3>

Greubel Forsey Tourbillon 24 Secondes Architecture

Movement: Manual winding Greubel Forsey caliber; 90-hour power reserve 
Functions: Hours and minutes, small seconds and 24-second tourbillon 
Case: 47mm (caseband diameter) and 45mm (bezel diameter); grade 5 titanium; water resistant to 50m 
Dial: Three-dimensional with variable geometry hour ring; Super-LumiNova filled indexes 
Strap: Black rubber; titanium folding clasp 
Availability: Limited edition of 11 pieces in 2022; thereafter, limited to 18 pieces per year worldwide from 2023 to 2025 
Price: CHF 440,000

For further information, visit <a href="https://www.greubelforsey.com/en">Greubel Forsey.</a> 
&nbsp;

Greubel Forsey Tourbillon 24 Secondes Architecture

Some hot-on-cold platinum-gold action, from the brand behind the most sophisticated (and aesthetically polarising) ‘travel’ watch of the last decade
&nbsp;

In all my years spent covering the watch industry, I can scarcely remember anybody who has rejected the possibility of wearing Greubel Forsey completely out of hand. I use the verb ‘wear’ because, for the vast majority of us hobbyists, the idea of actually owning and collecting watches which average a sticker price of US$600,000 (give or take) is sheer insanity. But that’s the beauty of ‘Editor’s Pick’: I get to choose just how much – or in this case how little – realism I want to inject into the picture.&nbsp;

Much like their astronomic price tags (easily 7-8 times what you’d pay for <a href="https://wristcheck.com/discover/editor's-pick/a-trio-of-patek-philippe-nautiluses-tiffany-signed">a certain jeweller-stamped sports watch </a>at the top of the market) , Greubel Forsey’s GMT pieces aren’t for everyone. Whereas most Swiss watch brands court the respectability that seems to accompany traditional horology, Greubel are the guys whom you can always count on to go full sicko mode: on every case, dial and movement that crosses their workbench – more Doc Brown than Louis Abraham Breguet. To my mind, the brand’s GMTs (more so than any other model) express the heart of this dynamic, where very serious, classically beautiful technique collides with a novel approach toward design and engineering, frequently bordering on the extreme.

&nbsp;
<img alt="greubel forsey" data-caption="Besides the GMT function, this watch features a worldtimer, power reserve indicator, a 3D globe and an inclined tourbillon" data-entity-type="file" data-entity-uuid="6a1fa51d-1d9a-47ae-8c30-cc3919346f91" data-image-style="blog_inline_image" height="1046" src="https://wc-strapi.s3.ap-east-1.amazonaws.com/article_import/images/92/20220103_wristcheck1879_1.jpg" width="1568" /><img alt="greubel forsey" data-caption="The 43.5 mm dial features a three dimensional globe with a bi-color 24-hour ring corresponding to each geographical area with the time" data-entity-type="file" data-entity-uuid="fd73ce22-473e-471f-98e1-0dc88e4f7f51" data-image-style="blog_inline_image" height="1046" src="https://wc-strapi.s3.ap-east-1.amazonaws.com/article_import/images/92/20220103_wristcheck1894_0.jpg" width="1568" /><img alt="greubel forsey" data-caption="The power reserve is shown on the arc at three o’clock and just next to it is the 24-second tourbillon that makes one rotation every 24 hours" data-entity-type="file" data-entity-uuid="ab3eff83-2c01-4cbe-937c-9e7239fb79f9" data-image-style="blog_inline_image" height="1046" src="https://wc-strapi.s3.ap-east-1.amazonaws.com/article_import/images/92/20220103_wristcheck1906_0.jpg" width="1568" />
&nbsp;

Despite the brand’s self-effacingly simplistic name for it, the Greubel GMT is anything but your bog-standard, two-timezone watch. The eponymous complication is in fact only the first in an arsenal of other features: including a worldtimer, power reserve, fully three-dimensional globe (that rotates once every 24 hours for good measure) and an inclined tourbillon. It is, in no small part, the reason why Greubel Forsey has become so synonymous with crafting watches that wear like miniature cities suspended under glass; and the experience of, for lack of a better word, experiencing the GMT (even if only for a few hours) is akin to inhabiting the perspective of some omnipresent, far-off martian – surveying another species from space.&nbsp;

Unsurprisingly, the popularity and distinctiveness of the GMT means that Greubel has made multiple versions since 2011. These range from the dressier incarnations that you’d expect (cast in a range of noble metals) up to the <a href="https://www.hodinkee.com/articles/greubel-forsey-gmt-earth-final-edition-2021">‘Final Edition’ </a>– a titanium send-off of the brand’s signature collection, released in a tidy 11-piece run last August. The broad contours of this ‘5N Movement’ version are consistent with other GMTs, meaning that if you hated that design to begin with – as some people on the internet appear determined to do – this is hardly going to subvert expectations. But beyond the admittedly bulbous protrusion that displays our planet’s natural rotation (in real time) and the vague appearance of being very information-dense, the GMT remains clever, audacious and in this instance, more than a touch reminiscent of the ‘hyper-complicated watch with an extravagant movement’ niche that has dominated indie collecting these past few years.

&nbsp;
<img alt="greubel forsey" data-caption="The caseback features a large disc that twists cities around a 24-hour ring.&amp;nbsp;As with all Greubel Forsey watches, the movement decoration is impeccable" data-entity-type="file" data-entity-uuid="e9a6ccb4-87bc-49c4-b6bb-8c8d740b1da3" data-image-style="blog_inline_image" height="1046" src="https://wc-strapi.s3.ap-east-1.amazonaws.com/article_import/images/92/20220103_wristcheck1930_1.jpg" width="1568" /><img alt="greubel forsey" data-caption="The watch's dial, movement base plate and bridges are finished in frosted rose gold" data-entity-type="file" data-entity-uuid="92a75d11-3c6d-45bb-b32d-fd5bb42748ee" data-image-style="blog_inline_image" height="1046" src="https://wc-strapi.s3.ap-east-1.amazonaws.com/article_import/images/92/20220103_wristcheck1882_0.jpg" width="1568" />
&nbsp;

As in previous incarnations of the GMT, the 5N version favours a movement that is obscured for the most part. This is as much a practical consideration as it is a quirk of design: with so many complications to nestle into a diameter that’s 43.5mm, the feature most visible to the naked eye is the movement’s mainplate – cast here in a pale, blushing hue of rose gold. The case technically isn’t two-tone, but that’s the comparison that has a tendency to emerge whenever I think about the 5N.&nbsp;

The rose gold adds warmth and contrast to what – in its most technical guise – can be an imposing mechanical exercise; and the addition of just one secondary colour opens up possibilities for all kinds of rubber and textile straps. That may sound an awful lot like misplaced enthusiasm in the broader conversation of a watch that costs as much as a two-bedroom apartment, but then again, we’re talking about what is essentially one of the most daring rethinks in how human beings perceive multiple instances of time, masquerading as a ‘travel watch’ with a self-esteem problem.&nbsp;

&nbsp;

<h3>Specifications</h3>

Greubel Forsey GMT Single Edition in Platinum

Case size: 43.5 mm 
Thickness: 16.14 mm 
Material: Platinum 
Water Resistance: 30m

Movement: Manual Winding 5 N 
Functions: Hours, Minutes, Small Seconds, GMT, World Timer, Rotating globe with universal time and day-and-night, Power Reserve, Tourbillon 
Frequency: 21,600 vibrations/hour 
Power Reserve: 72 Hours 
Strap: Rubber

This piece is available on <a href="https://wristcheck.com/buy/greubel-forsey/gmt-movement-5n-unique-edition-w00331jfogbf00">Wristcheck</a>.

&nbsp;

&nbsp;

&nbsp;

The Greubel Forsey GMT Unique Edition in Platinum

Can one watch tell the time everywhere on Earth? Well, the Greubel Forsey GMT certainly can
<h3>Born to Innovate</h3>

Founded by Robert Greubel and Stephen Forsey in 2004 on the simple premise that not everything in watchmaking had been invented already, Greubel Forsey has made its name as a watchmaker that continually seeks to push the envelope. Over 17 years later, GF stands as one of the best and most highly respected independent brands globally.

While brands all over the world regularly claim their inventions are revolutionary, innovative or just plain new, we often find that is only sales talk. In an industry filled with recycled designs, recycled mechanics and, at times, a lack of demand for fresh ideas from a community that is drunk in the echo chamber of social media, Greubel Forsey are a breath of fresh air. Trying something different and challenging the status quo is what makes this Indie tick.
<img alt="Greubel Forsey GMT Earth White Gold" data-caption="Greubel Forsey GMT White Gold" data-entity-type="file" data-entity-uuid="02fb179d-0e3f-4b55-965c-7bcfd86cbf3c" data-image-style="" src="https://wc-strapi.s3.ap-east-1.amazonaws.com/article_import/images/17/_0002_593A1652-2_0.jpg" />
<h3>&nbsp;</h3>

<h3>Shaking the industry to its core</h3>

Built on the necessity to embrace their previous limits, we know that Greubel Forsey means it when they say they have created something that we haven't seen before. With that, when Greubel Forsey released their latest version of the GMT Earth in 2018, the industry perked its collective ears and paid attention to what they had created.

While the GMT&nbsp;has a hilariously modest name compared to what other watchmakers name their watches, it is without a doubt one of the most complicated watches the brand has ever made. Before I even tackle getting into the complications, just looking at the dial can be tiresome with its complexity level being enough to fry brains. Seriously, look at the dial and soak it in. This is peak 21st-century horology, and for&nbsp;good reason.

&nbsp;
<img alt="Just looking at the dial can be tiresome with its complexity level being enough to fry brains" data-caption="Just looking at the dial can be tiresome with its complexity level being enough to fry brains" data-entity-type="file" data-entity-uuid="2d07875f-b2d2-4665-898f-fedf681d7b22" data-image-style="" src="https://wc-strapi.s3.ap-east-1.amazonaws.com/article_import/images/17/593A1576-2.jpg" />
<h3>&nbsp;</h3>

<h3>Functionality and Design</h3>

Starting with the simplest of functions, the GMT's overall dial layout begins with a sapphire dial at 2 o'clock indicating hours and minutes in local time with a small seconds subdial incorporated within it, with a power reserve indicator found just beside it. At 10 o'clock lies a red triangular hand that indicates a second timezone and is operated via a pusher at 10 o'clock on the case. This rounds off the more 'conventional' complications on this incredible timepiece.

Filling the bottom half of the GMT's display lies the artistry that makes this piece so unique, and where it gets its name. Starting with the 4 o'clock position, we have a 24-second inclined tourbillon. The tourbillon is inclined to ensure that the tourbillon is never in either extreme position: perfectly vertical or horizontal. Next, we have a 3D model of the Earth that we call home (not the watch itself, albeit that would pretty meta). This model Earth rotates in real-time and thus provides a view of the universal time around the globe, acting as a sort of world-timer.
<img alt="A 24-second inclined tourbillon at 4 o'clock position" data-caption="A 24-second inclined tourbillon at the 4 o'clock position" data-entity-type="file" data-entity-uuid="99533898-2de3-4e1c-a918-87653d7fec87" data-image-style="" src="https://wc-strapi.s3.ap-east-1.amazonaws.com/article_import/images/17/593A1575-3-2_0.jpg" />
While not too accurate, with the model Earth we can figure out the approximate time from anywhere within view by drawing a line through the region to the hour ring that encircles the globe. This ring also provides a quick day and night time visual through the use of its two-tone nature, much like a conventional two-tone GMT bezel.
<img alt="A 3D model of the Earth rotates in real-time and thus provides a view of the universal time around the globe" data-caption="A 3D model of the Earth rotates in real-time and thus provides a view of the universal time around the globe" data-entity-type="file" data-entity-uuid="681c3f0f-4632-4a9e-95fb-83dccac08e3b" data-image-style="" src="https://wc-strapi.s3.ap-east-1.amazonaws.com/article_import/images/17/_0010_593A1688_0.jpg" />
Moving to the caseback, the complications continue with a 'real' worldtimer that provides a more accurate reading for 24 different cities across the globe. Differentiating cities that observe summertime by marking them silver and those that don't in black, we can read the times for the listed cities no matter the time of year — summer or winter — by reading off one of the two 24-hour rings. Sitting next to the worldtimer is an engraved sun, a signature for the Greubel Forsey GMTs.
<img alt="Reading for 24 different cities across the globe on case back" data-caption="Reading for 24 different cities across the globe on case back" data-entity-type="file" data-entity-uuid="63dbb3f8-234d-4c51-86aa-e012448b4104" data-image-style="" src="https://wc-strapi.s3.ap-east-1.amazonaws.com/article_import/images/17/_0006_593A1590-2_1.jpg" />
<h3>&nbsp;</h3>

<h3>Construction and Aesthetics </h3>

Finally dragging our gaze beyond the complexity of the mechanics that lie at the heart of this incredible piece of work, we can look at the beauty of the GMT's construction. Sitting within a 45.5mm white gold case, the GMT&nbsp;is not a conventionally shaped watch. Bulging at 7 o'clock to accommodate the globe sitting there, we begin to understand just how unique this timepiece is.
<img alt="An exceptionally shaped watch" data-caption="An exceptionally shaped watch" data-entity-type="file" data-entity-uuid="d769c42a-0e5f-43d3-8512-77f7b43cd28c" data-image-style="" src="https://wc-strapi.s3.ap-east-1.amazonaws.com/article_import/images/17/_0004_593A1592-2.jpg" />
Featuring a bezel "engraved [with] inscriptions that encapsulate the key values of Robert Greubel and Stephen Forsey" as the brand says, the GMT&nbsp;does not allow your eyes to rest for even just a moment. Visual intrigue galore, out-of-this-world finishing and a hypnotic duo comprising a 24-second tourbillon and a rotating model Earth, the Greubel Forsey GMT seems to defy logic, yet there it lies.