The Breguet Marine Tourbillon Equation Of Time ‘Marchante’ In Platinum: Chasing The Sun

The Breguet Marine Tourbillon Equation Of Time Marchante ref. 5887 was first introduced by Breguet in 2017 and it was then, as still is, a horological heavyweight in every sense of the word. The 5887 was first introduced in platinum and now exists in four models in the catalog, in both platinum and rose gold, and it combines the tourbillon, the perpetual calendar, and the Equation of Time. How these three complications came together in a single, 43.9mm x 11.8mm watch, is a story that has as its main cast of characters an extra flat peripheral rotor automatic tourbillon, the perpetual calendar complication, and a most unusual version of an unusual, esoteric, and horologically beautiful version of the Equation of Time – the Equation of Time Marchante.

The Perpetual Calendar

The perpetual calendar as a complication is well known – a perpetual calendar is a watch which always switches on the correct date at the end of every month, including months with 30 or 31 days, and also on the 28th of February (and on the 29th in a Leap Year). On the Breguet Marine EOT, the date is shown on a retrograde display by a hand tipped with an anchor (like the watch, this is a nod to the fact that Abraham Louis Breguet was appointed Horloger Marine by King Louis XVIII in 1815, after the Revolution and the Napoleonic Empire gave way to the restoration of the House of Bourbon as the kings of France in 1814, just in case you’re not up on the Machiavellian twists and turns of French history at the dawn of the 19th century.

The day of the week and the month are show in apertures on the upper left and right hand sides of the dial, with the tourbillon visible through an aperture at 5:00 – also visible is an odd-looking kidney shaped cam, which is the cam for the Equation of Time. The hand for the Equation of Time is tipped with a golden Sun, and the hour, minute, retrograde date, and EOT hands all run from concentric pivots at the center of the dial.

It’s easy to miss, but there is also a very discreet power reserve indication at 7:00, which the ref. 5887 inherits from the tourbillon base caliber. And there is an even more discrete leap year indicator, in the form of a disk with the numbers 1-4 hidden away just to the right of the month in the month window.

The Tourbillon

The watch is built around an unusual movement. The movement in the Marine EOT Marchant is Breguet caliber 581 DPE, but the base movement, if you can call it that, is the caliber 581 DR, which is found in the Classique Tourbillon Extra-Plat 5337.

This is an extra flat (hence, “extra-plat”) tourbillon movement, launched in the ref. 5337 in 2013 and the cal. 581 DR is just 3mm thick.

The winding mass is set on a peripheral rotor with inward facing teeth, which gears to the automatic winding train and you can see the same layout in the 5887 EOT, caliber 581 DPE. The inner edge of the peripheral rotor rides on three ball bearings, just visible at the edge of the movement at roughly 4:00, 8:00, and 1:00. The wave-engraved winding mass is solid platinum. The engraving on the lower tourbillon bridge, BREVET DU 7 MESSIDOR AN 7, refers to the date of Breguet’s patent grant for the tourbillon in the Republican calendar briefly, and unsuccessfully, adopted by the Republic.

Caliber 581 DPE, as seen in the Marine EOT Marchante

The engraving on the movement bridges differs in the two watches – the 5337 has an abstract, somewhat floral pattern but the engraving on the back of the EOT Marchante is a spectacular rendering of the stern of the Royal Louis, which was a French 110 gun ship-of-the-line, later renamed Républicain (for obvious reasons). She was in the line of battle at the Battle of Ushant, in 1778 and eventually ended, somewhat ignominiously for a proud fighting vessel, grounded at Brest in December of 1794, where she broke up in a storm.

Somewhat more relevantly for our purposes, you can see that at least from the back the two movements are virtually identical, with the exception of an extra jewel on one of the bridges in the 581DPE, and that Equation of Time cam. The overall jewel count is much higher, though – 42 jewels for the 581 DR versus 57 for the 581 DPE, most of which I imagine are associated with the EOT Marchante and perpetual calendar mechanisms.

The perpetual calendar works are almost invariably located under the dial in perpetual calendar watches and so it is in the 5887. Under the dial work is collectively referred to as cadrature in watchmaking. Here we can see the pivots for all four of the centrally mounted hands at the center of the dial, as well as the day and month disks and that little four year Leap Year disk, hidden under and to the right of the month disk.

The Equation Of Time

Now we get to the juicy part – the Equation of Time Marchante. To understand the complication, let’s look at three different definitions of a day: the true solar day, the mean solar day, and the civil day.

The Equation of Time is not complicated although it does involve some ideas most of us don’t usually think about. The big one is that days are not the same length throughout the year – specifically, the true solar day is the time it takes for the Sun to return to the same point in the sky (you can pick any point, the point when the Sun is highest in the sky – true solar noon – is conceptually convenient). For several reasons, including the fact that the Earth’s orbit is not a perfect circle, as well as the inclination of the Earth on its axis, this time is on average 24 hours, but depending on the date, a clock showing between mean solar time (that is, a 24 hour average day) can be as much as 16 minutes and 33 seconds fast, slow by as much as 14 minutes, 6 seconds. This difference is the Equation of Time.

Often, clockmakers pasted a table for the Equation of Time inside clock cases; the table showed on any given day how much ahead or behind mean solar time, the true solar time was for that day. To set your clock, all you had to do was check the time on a sundial, and then add or subtract the Equation of Time for that day; your clock would then show the correct mean (average) solar time, for a 24 hour day. Nowadays, local mean solar time has been superseded by civil time, which is the time across a time zone; this is determined by the number of hours difference between that time zone and Greenwich Mean Time. How accurate your Equation of Time complication is, depends on where you are in your time zone. If you are on the central line of longitude for your time zone, then the difference between mean solar time and civil time, according to the US Naval Observatory, will be about 0.9 seconds. This means if you own an Equation of Time watch, and you live in New York City, you’re really in luck; the central longitude meridian for EST is 75º West, and New York is only spitting distance away, at 74º West.

Here’s a recap:

• True solar time: the time it takes for the Sun to return to a given position in the sky
• Mean solar time: the average of true solar time over a year (24 hours)
• Civil time: the time for a given time zone; only matches mean solar time at the center meridian of longitude of the time zone

Usually, the Equation of Time is shown by a hand that shows how fast or slow civil time is with respect to mean solar time – as seen on the out of production Breguet 3477.

Breguet 3477

Here the Equation of Time is visible in a sector at the upper right, rounded off to ±15 minutes over the course of a year.

The Equation of Time is handled mechanically by a cam shaped like a somewhat lumpen potato, which rotates once per year. The tip of a lever mounted on a rack rides on the edge of the cam and translates its rotation into the back-and-forth motion of the EOT hand – hence the cam visible through the aperture on the dial of the Marine EOT Marchante.

The Equation of Time Marchante

“Marchante” means “walking” in French. In an Equation of Time Marchante, the difference between civil time and solar time is shown by an EOT hand which rotates once per day along with the minute hand, but which shows the Equation for that day by how far ahead or behind the minute hand it is running – that is, the EOT hand “walks” along with the minute hand around the dial. Four times per year, when the Equation is zero, the minute hand and EOT hand will be superimposed. You can also think of an EOT marchante hand as a sort of true solar time minute hand.

The Equation of Time Marchante is pretty rare in wristwatches. The first company to introduce it was Breguet’s sister brand, Blancpain, which launched the Equation of Time Marchante in 2004, in the Le Brassus Equation Marchante. The Marchante complication took the form of a module, and you can peek under the hood for a look at the Equation cam and perpetual calendar works as implemented by Blancpain in the Villeret Equation of Time Perpetual Calendar over at The Naked Watchmaker.

The different scales of time that the watch displays cover everything from seconds to the full four year Leap Year cycle, and in keeping with the “marchante” theme, there is also a continuous indication of the months. The letters for each month are the first letter of the month in English and the disk rotates counterclockwise, with the current month shown adjacent to the triangle at 12:00.

One other thing you’ll notice is the escape wheel, which is just visible in the lower left quadrant of the aperture. It’s in silicon, as is the escape wheel, and these are of course materials which are more or less totally unaffected by magnetic fields – this isn’t a Master Chronometer of course, but it’s a nice plus in modern watchmaking. I miss somewhat the more artisanal approach to escapement components – there is something compellingly beautiful about a hand polished escape wheel and lever, with a hand formed overcoil balance spring but the truth is, balance springs (for instance) have been at least somewhat an industrial product ever since the introduction of Nivarox-type alloys in the 1930s, so that ship sailed a long time ago, to make a weak contextual joke.

So there you have it – a watch that combines a complication first introduced by Blancpain in 2004, with an extra flat peripheral tourbillon mechanism first introduced by Breguet in 2013, in a watch with a perpetual calendar launched in its first version in 2017. Despite its complexity the whole thing remains pretty flat, thanks to the peripheral rotor on the base movement, giving the watch despite its size and heft, a certain grace as well.

The Marine line are nominally sports watches but they have always seemed to me to take the whole idea of a sports watch as nothing more than a point of departure. The case is water resistant to 100 meters, sure, and well it should be with the name Marine attached to the line, but this is an extremely elevated watch technically with a very deep backstory, and its unapologetic opulence and celebration of old-school watchmaking values, supported by newer technical materials and features, reminds me of nothing so much as a modern sailing yacht – something for which modern engineering and materials are important, but whose sex appeal lies in the embodiment of a more ageless, timeless kind of romance.

The Breguet Marine Tourbillon Equation Marchante, Ref. 5887PT/92/5WV: Case, platinum, 43.9mm x 11.8mm, 100M water resistant with fluted case band, sapphire crystals front and back; dial, white gold with black finishing and hand-guilloché wave motif with 18k gold rhodium plated calendar windows; hands, rhodium plated 18k gold. Movement, Breguet caliber 581 DPE, 16 1/2 lignes (37.27mm) 563 components running in 57 jewels at 28,800 vph; silicon balance spring, escape wheel, and lever with 80 hour power reserve from a single mainspring barrel. Engraved with Royal Louis ship motif and compass rose on the mainspring barrel. Tourbillon cage in grade 5 titanium. Price, $270,000. The 1916 Company is an authorized retailer for Montres Breguet.