The automatic deck chronometer in the Marine line has been inspired by the famous deck chronometers used by sailors to check the time indicated by the on-board chronometer

Appointed official watchmaker to the Naval Ministry in 1835, Leroy held this prestigious title for longer than any other company in this field. Supplying more than thirty royal, imperial and national navies, as well as many merchant and military fleets around the world, the company produced more than 2,200 chronometers of all types dedicated to precision time keeping at sea before the introduction of radio-controlled and computer clocks.”

About Leroy the brand:
Leroy was founded in 1747 and is the oldest of all the top watch manufactures. In fact, it is older than Patek Phillippe, Vacheron Constantin, Breguet, and Audemars Piguet. Leroy has a venerable royal history. By 19th century, it was the most prestigious watchmaker in Europe. Appointment royal watchmaker by Louis 15 and Queen Elizabeth and King of Portugal.
Throughout history, countless famous historical figures were clients of Leroy’s pocket watches and watches, as recorded in the company register. Owners of Leroy watches include, among artists and literary figures, Debussy, Chopin, Proust, Alexandre Dumas, Wagner, and Matisse; among statesman, Alphonse de Lamartine, Napoleon III, General De Gaulle, General Eisenhower, Roosevelt, and Churchill. Other famous clients include Alfred Nobel, St. Exupery, Lindberg, Paul-Emile Victor, Marcel Dassault, and the list goes on…
Historically, Leroy was far more famous, precious and horologically important than Breguet, as the premier choice for royalties.
About the technique of hand-guilloche used on all Leroy watch dials:
Astonishing in its beauty and precision, guilloche is one of watchmaking’s rarest art forms. Engraved patterns interlace, creating lines often so fine that they are barely visible to the naked eye. Created using a rose engine that dates back to the late 19th century, each line of guilloche is crafted by a master engraver, who skillfully controls the speed and pressure of the rose engine to ensure the flawless depth and symmetry of the pattern, representing traditional watchmaking excellence at its most exquisite. Those few master craftsman with the patience, dexterity and passion necessary to master the craft are as rare a breed as the rose engine themselves. Today, Switzerland has less than 10 full-time guillocheurs. Leroy especially champions and aims to preserve the art of guilloche and does that on all of its watch dials, as well as on automatic rotors with open display backs. No expense is spared in making these exquisite dials.

Crafting watches only in precious metal, Leroy has a very Small annual production of 100 – 150 pieces a year, often sold directly to private clients through high-end dealers. The brand has never been discounted.
The brand is a rare collaboration between the Swiss and the French. Two ateliers located in Bienne, Switzerland, and Besancon, France – the cradle of high watch-making in France.
Perfect harmony in traditional watch-making techniques, involving painstaking-attention to detail, classic guilloche on dial, flawless polishing of the case.
Each watch takes hundreds of hours to craft, hand-finish and regulate. The movements involve beautiful finishing and fine-tuning to the standards of National Observatory of Besancon, known for being the gold standard for precision. These models come with the Besancon certificate
Leroy only makes watch in precious metal, never in steel.
Consistent with Leroy’s value for highest level craftsmanship. All Leroy timepieces come in a heavy and luxurious wooden box crafted by one of the best high-end cabinet makers in the world, and hand finished. It is lined with leather, with golden metal hinges.

Please check out this video link for a documentary about the history of Leroy brand.
https://www.youtube.com/watch?v=EGnZ9xbEd6g
The movement (calibre) of the deck chronometer has been manufactured in the Vallee de Joux, in the heart of the Jura mountains of Switzerland. Each part of the movement is then assembled, regulated and finished in Besancon, France, by the master watchmakers of Les Ateliers Leroy.

Each Leroy Marine Automatic Deck Chronometer undergoes a series of checks at the Observatory of Besancon. Contrary to the COSC certification, which tests the rating precision of the movement only, Leroy has its watches certified in their entirety. It tests the watch “heads” individually for 16 consecutive days, in five different positions and at three different temperatures. The results are compared with the atomic clock of the Observatory. This certification testifies to the high degree of precision and smooth operation of the watch tested. The “Bulletin de marche de Chronomètre” (chronometer rating certificate) is granted only to watches having successfully passed the trials conducted in accordance with the ISO-3159 norm. Besançon Observatory is one of the few accuracy testing institutes in the world entitled to grant this certification. Within the watch industry, the “viper’s head” hallmark of the Observatory has indeed been a token of accuracy since 1897.