Thomas Mercer Chelys Chronometer in Partnership with Winch Design and Marmor Hotavlje

Thomas Mercer, Marmor Hotavlje and Winch Design present their latest collaboration – Chelys, an horological sculpture fusing the respective arts of marine chronometry, stone carving and yacht design.

Established in 1986 by Andrew Winch and his wife Jane, Winch Design has grown to be an award-winning multi-disciplinary design studio. The design teams at Winch work tirelessly to create dream, bespoke homes, on land, in the air and at sea. With the focus on extremely high-end, dynamic design for a worldwide client base, Winch Design is recognised as a globally leading studio and has established itself as the go-to for individuals who expect not only the highest levels of design excellence but also a real understanding of how they want to live their lives.

Established in London in 1858, Thomas Mercer is a name forever synonymous with the marine chronometer, the timekeeper invented for determining longitude at sea. Today the company diligently and proudly upholds the tradition of British clock-making by manufacturing exclusive marine and table chronometers that grace the interiors of the finest yachts and residences.

Led by the Selak family, Marmor Hotavlje is one of the foremost stone-cutting companies in the world. In 1721, the residents of the small Slovenian village of Hotavlje discovered the riches hidden in their mountains and carved their first stone. Thus began a rich tradition, which, through generations and generations of stone-cutters, transmits knowledge, skills and love for their craft. In 1948, the workshops at the foot of the quarry joined the Marmor Hotavlje company whose pride today in its history and heritage parallels its excellence in a variety of international projects.

The word Chelys derives from the Latin form of the original Ancient Greek χέλυς (tortoise) which describes a musical instrument made of a shell, its convex form resembling that of this fine chronometer. According to the fable of his Homeric Hymn, Hermes found a tortoise near the threshold of his mother’s house and decided to hollow out the shell to make the soundbox of a seven-stringed instrument, thus inventing the first lyre of the Ancient Greeks.

The sinuous and sophisticated lines of the Chelys are carved out of ivory onyx, a semiprecious white natural stone with immaculate crystalline background and evocative waves undulating through its structure. Named after the Ancient Greek word “ὄνυξ” (nail), legend says that one day Cupid clipped the godly nails of Venus with an arrow-head while she was sleeping, and the Parcae (the three daughters of Zeus) transmuted them into stone, so that no part of the divine body could ever be destroyed. Rare and precious, it has been considered a luxury staple since ancient times. Measuring 44x39x22 cm and weighing 25 kilos, this sculpture is crafted through a meticulous process using traditional hand stone masonry, impeccably executed by Marmor Hotavlje’s skilled artisans.


With a case inspired by a mythological musical instrument, the movement had to mirror it in greatness, and its melody no exception. Like every Thomas Mercer mechanism, the new calibre TM8004 sports the sine-qua-non specifications of a marine timekeeper including the special spring detent escapement. Also known as the “chronometer escapement”, the spring detent is distinguished by its rare one impulse per oscillation, resulting in its individual – and very appropriate for the occasion – sound, featuring one loud and one soft beat.

Among the other subtleties of this precision timekeeper, note the ovalising balance for thermal compensation and the beautiful chain-fusee drive. The horological equivalent of an infinitely variable gearbox-speed, the latter equalises the waning force of the mainspring by delivering the mechanism an ever constant amount of energy. As the force decreases, the chain moves from the top to the base of the cone, increasing its leverage to keep the torque constant.

The movement is housed in a tube case made of extra-white crystal, offering an all-around view of the inner workings which can be admired in their entirety. The elegant open-work dial magnifies the intricacies of the multi-complicated movement and its stone setting pairs perfectly with the onyx body. The hands are steel-made, hand-finished with bluing technique.

A truly unique celebration of horology, design and stone-carving, Chelys will be unveiled at Monaco Yacht Show 2019 – indisputably the leading event of the superyacht industry – held in Monte Carlo from the 26th to the 29th of September.

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