The equation of time is one of the most difficult complications to implement inside a wristwatch, since it requires a means of indicating both mean solar time (a 24-hour day) and true solar time (the actual time it takes for the sun to appear at the same point in the sky relative to the observer after the Earth has completed one full revolution about its axis). In most cases, the equation of time is displayed on a separate scale graduated from -16 minutes to +14 minutes, showing the difference relative to mean solar time but leaving the wearer to calculate the actual true solar time based on the mean solar time displayed by the watch’s minute hand. The running equation of time complication, on the other hand, is offered by only a handful of the most traditional watch companies with 200-year-plus histories and shows both times at a glance on hands affixed to the same central axis.
In technical terms, the equation of time function is “calculated” by a very specifically bean-shaped cam that can take into account the analemma curve that represents the Earth’s orbit around the Sun over the course of a year. This cam is coupled with a feeler-spindle that converts its rotation into the movement of a second central minutes hand to show the true solar time. Unusually for an equation of time complication, this crucial component has been given pride of place on top of the tourbillon carriage, mounted on a sapphire disc engraved with the months of the year. Although the exact date is already visible on the dial thanks to the Marine Equation du Temps 5887’s perpetual calendar, the graduations on the sapphire disc allow for easy adjustment of the equation of time function.
Breguet has opted to introduce a new design for the Marine models with this new flagship piece. The deep blue dial, with a solid-gold base, has a brand-new engine-turned decoration developed specifically for this model, symbolising the ocean waves. The signature gold Breguet hands are infilled with SuperLuminova, complemented by SuperLuminova appliques positioned above the applied Roman numerals on a satin-brushed chapter ring. The running equation hand is in blued steel and has a delicately facetted golden sun, while a fourth central hand, with an anchor tip, is used for the retrograde date of the perpetual calendar. A second type of wavy engine turning is used on the blue outer circumference of the dial.
The focus on the dial side is on clear legibility, to such an extent that the aperture showing the bean-shaped cam and tourbillon carriage has been displaced slightly to 5 o’clock, allowing for a larger diameter than if it had been located in the usual 6 o’clock position. The case back, on the other hand, is a testament to the tradition of hand finishing and engraving at Breguet. The rear side of the tourbillon bridge is engraved with the date of Abraham-Louis Breguet’s patent, as a reminder that he invented this particular complication. The remaining bridges have been painstakingly engraved by hand with an image of the Royal Louis, a first rank vessel in the French Royal Navy. The decoration is completed by a marine compass motif on the barrel housing.
Timekeeping is provided by the Breguet calibre 581DR, which has a 60-second tourbillon coupled with a silicon balance spring, silicon escape wheel and silicon pallets. The lightweight titanium tourbillon carriage allows for a highly respectable 80-hour power reserve, which is indicated in a discreet aperture between 7 and 9 o’clock on the dial side and maintained by a peripheral winding rotor so that the beautiful caseback engraving remains visible at all times.
The Breguet Marine Equation Marchante 5887 model is available with a 43.9mm diameter case in 950 platinum or 18-carat rose gold – the former with a blue dial and rhodium-plated movement, the latter with a silvered dial and anthracite-finished movement.