Market Watch: Vacheron Constantin Mercator Prototype Pièce Unique

Offered by the enameller himself.

An unusual wristwatch with twin retrograde hands in the form of a compass, the Mercator was unveiled in 1994 for the 400th anniversary of the death of Gerardus Mercator (1512-1594). A pioneering cartographer famous for inventing the map projection that evolved into the world maps of today, Mercator was born in present-day Belgium, which is where the genesis for the Mercator wristwatch was formed.

The Mercator wristwatch was unusual amongst watches of the 1990s, being one of the rare handful of classically styled watches with an unconventional time display. At the same time, the fanciest versions of the Mercator watches featured hand-made fired enamel dials, which were rare at the time. The entry-level versions, in contrast, had acid-etched brass dials sporting similar motifs.

A tribute to the past

The Mercator watch was the brainchild of Jean Genbrugge, an artisan who, along with his wife Lucie, specialises in miniature enamel painting. Mr Genbrugge is also a watchmaker, which led him to invent the Mercator retrograde mechanism, while also devising the map-pattern dial as in a nod to his homeland’s famous son.

“I am a citizen of Antwerp like Mercator, and I have a great admiration for his scientific work,” recounts Mr Genbrugge, “When the 400th anniversary of Mercator’s passing took place in 1993, I visited the exhibition in honour of his life at the Mercator Museum in Sint-Niklaas.”

“Being a sailor, I am a navigator myself,” explains Mr Genbrugge, “Which gave me the idea to create a homage to Mercator – a special watch with an enamel dial showing the map Mercator created himself for the New World, or north and south America.”

Two pages from a book about Mercator that Mr Genbrugge used as a reference for the project; the watch dial reproduces the map above. Photo – Jean Genbrugge

“My plan was to build a small series of watches for collectors, but after I spoke to my friend Helmut Crott, he suggested I contact Vacheron Constantin. Helmut had a good relationship with the head of VC then, Claude-Daniel Proellochs, so we went to present our project to him. Claude-Daniel was fascinated by the idea right away, and that started a longstanding and friendly relationship that lasted till the day Claude-Daniel left VC.”

The watch Mr Genbrugge built as a sample for Proellochs is the very first Mercator wristwatch prototype, the very watch pictured here. Now in his sixties, Mr Genbrugge is offering the prototype for sale, via a dealer in Luxembourg, along with the sketches and technical drawings for the movement and dial.

The watch and its associated documents

Using the Vacheron Constantin cal. 1120 as a base – derived from the Jaeger-LeCoultre cal. 920 and also known as the Audemars Piguet cal. 2120/2121 – Mr Genbrugge constructed a bi-retrograde mechanism that went on top of the base movement.

The subsequent limited-edition Mercator had an identical time display, but one driven by a retrograde mechanism modified by Vacheron Constantin for more efficient serial production.

The cal. 1120 under the display back that was painted with a tiny sailboat by Mr Genbrugge, a detail absent on the production version

The gold case of the prototype is identical to that found on the Vacheron Constantin perpetual calendars of the period, making it distinct from the standard Mercator, which had a slightly more elaborate case featuring a stepped bezel and lugs with fluted edges.

Requiring some two months to produce according to Mr Genbrugge, the centrepiece of the watch is similarly unique on the prototype. Bearing Mercator’s famous world map in miniature enamel, the dial has subtle differences with the serially-produced version, including the artists’ signature, which reads “J.& L. Genbrugge – Antwerp” on the prototype, while the standard dial did away with the city name.

Importantly, the watch is accompanied by a letter signed by Claude-Daniel Proellochs, then the chief executive of Vacheron Constantin. Respected for having helped rebuild Vacheron Constantin after the Quartz Crisis, the late Proellochs led the company from 1988 until his retirement in 2005, which was also the year the brand celebrated its 250th anniversary in grand style.

Dated 1996, the letter notes that the Mercator in question is a prototype that was used to “develop the Mercator series, though the production model was different in its final form”. It ends by saying the prototype is the “property of Mr Jean Genbrugge”.

The success of the Mercator watch led the Genbrugges to become dial makers for a variety of watch brands, including Piaget and Bovet. They continue to do so today, producing hand-made enamel dials that are half the height of industrial average, at about 0.5 mm, compared to about 1 mm for the typical enamel dial.

The Mercator prototype has been consigned for sale at Watch Collector in Luxembourg by Mr Genbrugge, and priced at €175,000.

Addition March 11, 2021: Inclusion of comments and photos from Jean Genbrugge.

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Roger Dubuis Debuts the Excalibur Spider 39 mm

The signature style but more wearable.

Known for its bold, big, and skeletonised watches, Roger Dubuis is paring back its extravagant style – just slightly – with two smaller, 39 mm versions of the Excalibur Spider. Limited to 88 pieces in each guise, the Excalibur Spider 39 mm retains the brand’s signature Celtic-cross flying tourbillon and the open-worked case of the lightweight Spider series.

In addition to the twin Spider models, the new 39 mm size also includes an edition created in collaboration with Italian tyre maker Pirelli, the Excalibur Spider Pirelli that’s limited to just 28 watches.

Initial thoughts

With the same aesthetic found on earlier Excalibur watches, which were either 45 mm or 47 mm, the new 39 mm models are practical rather than innovative. And the RD510SQ skeleton flying tourbillon movement already exists, found inside the 36 mm Excalibur watches for women.

What’s new is the 39 mm case, which makes the Excalibur substantially more wearable. The new case is undoubtedly a commercial decision, since the line between watches for each gender gets increasingly fuzzy.

The Excalibur Spider 39 mm Pirelli

More women now want larger watches, while men sometimes revert to case sizes that are more old-school 20th century than 21st. During the online launch of the 39 mm models, Roger Dubuis chief executive Nicola Andreatta noted that the 36 mm Excalibur watches were a surprise hit amongst male clients in Japan, despite being marketed as ladies’ watches.

The 39 mm Excalibur Spider fills a sweet spot without reinventing the wheel. So if you’re a fan of the Roger Dubuis Excalibur but have long found them too large, the 39 mm models are worthy of of consideration.


The standard 39 mm Excalibur Spider is offered in two case styles: titanium or pink gold with white accents.

The more masculine of the two, the titanium version has a diamond-like carbon (DLC) coated case middle with rubber inlays, and a brushed titanium bezel. It’s a subtle fusion of titanium and rubber, making it the most understated of the trio.

More feminine but not specifically a ladies’ watch is the version in pink gold with white rubber inlay. It’s accented with brilliant-cut diamond hour markers on the open-worked ceramic flange, while doing away with the honeycomb mesh found on the other models. The result is a more flamboyant and less technical appearance. This makes more of a statement than the other versions, and being precious metal with diamonds, it is also the most expensive.

And the sportiest of the three is the Excalibur Spider Pirelli 39 mm. This has a blacked-out aesthetic that’s all DLC-coated titanium with red rubber accents.

Exclusive to Roger Dubuis boutiques, it is fitted to a strap inlaid with actual rubber from Pirelli tyres taken from the winning cars in auto races. Despite the small edition run and the Pirelli-rubber bonus, this costs exactly the same as standard Excalibur Spider in titanium.

All three watches are powered by the same RD510SQ, a hand-wound, in-house movement with its bridges and base-plate open-worked in Roger Dubuis’s trademark star motif. The centre of the largest star is the mainspring, while the smaller star underpins the flying tourbillon. And as with all of the brand’s mechanical watches, the Excalibur Spider 39 mm is hallmarked with the Poinçon de Genève, or Geneva Seal.

Key Facts and Price

Roger Dubuis Excalibur Spider 39 mm
Ref. RDDBEX0815 (titanium)
Ref. RDDBEX0816 (pink gold)
Ref. RDDBEX0817 (Pirelli edition)

Diameter: 39 mm
Material: Titanium or pink gold
Crystal: Sapphire
Water resistance: 50 m

Movement: RD510SQ
Functions: Hours, minutes, and flying tourbillon
Winding: Manual-winding
Frequency: 21,600 beats per hour (3 Hz)
Power reserve: 60 hours

Strap: Rubber strap with quick-release mechanism

Limited edition: 88 pieces each; Pirelli edition 28 pieces
Availability: Boutiques and authorised retailers
Price: US$159,500 (Pirelli and titanium), US$182,500 (pink gold)

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