Maurice Lacroix Masterpiece Mysterious Second: what does its owner think?

The Maurice Lacroix Masterpiece Mysterious Second, launched in 2013, is a mechanical watch conceived around a deliberately unusual way of representing the passage of seconds. Also known by its French name Masterpiece Seconde Mystérieuse, it follows experimental pieces such as the Masterpiece Square Wheel Seconds but replaces visible geometric gearing with an illusion of levitation. Hours and minutes are grouped into an off-centred display around 2 o’clock, while a large disc dedicated to the seconds occupies the lower part of the dial. A two-ended hand appears to move freely across this display, alternating between horizontal and vertical readings in fifteen-second sequences.

The 43 mm stainless-steel case houses the automatic ML215 calibre, the twelfth movement developed by Maurice Lacroix at the time. With its partially skeletonised construction, sapphire caseback and initially limited production, the model clearly prioritises mechanical theatre over discretion.

Design & legibility: the seconds become the main spectacle

A conventional watch generally treats the seconds as secondary information through either a thin central hand or a discreet small-seconds display. The Masterpiece Mysterious Second completely reverses this hierarchy. Hours and minutes are deliberately moved towards 2 o’clock to release a large area for the seconds. The latter move across a disc carrying linear markers arranged rather like a crosshair. The seconds hand that appears to float and change direction every fifteen seconds forms the fundamental distinguishing feature of the model. During one minute, its reading alternates between horizontal and vertical axes. The result requires a short period of adjustment: an eye accustomed to following a hand around a circle must understand a motion that appears both linear and rotational. This difficulty is part of the intended experience and turns an extremely simple piece of information into a permanent mechanical animation.

The illusion is created through the combination of the seconds disc and the hand mounted at its centre. When observed without understanding the mechanism, the hand seems detached from any visible pivot and appears to move freely above the dial. The disc itself participates in the motion while the hand rotates around its own axis to maintain the reading against the different markings. The complication plays more with the perception of movement than with the quantity of information displayed. There is no chronograph, complicated calendar or second time zone: nearly all the sophistication lies in the way a second is represented when it could normally be displayed far more simply. This choice explains the Mysterious Second name and places the watch within a horological tradition in which mechanical illusion becomes spectacle while remaining produced by mechanical components visible around the device.

The remainder of the dial is partially skeletonised and reveals a substantial part of the bridges and architecture of the ML215. This opening is deliberately asymmetrical: the small hours-and-minutes display occupies the upper-right area, the large seconds disc dominates the lower half and mechanical openings appear around both elements. Early versions use either rhodium-plated bridges or a darker ruthenium treatment. Metallic blue hands provide particularly strong contrast on the lighter configurations. The deliberately asymmetrical composition makes straightforward time reading secondary to discovering the movement. This approach may appeal strongly to an enthusiast who enjoys visible mechanics but will be less appropriate for someone seeking the instant legibility of a classical three-hand watch. The Mysterious Second makes no attempt to hide this priority: its dial is conceived as a mechanical stage before being a minimalist instrument.

Case, strap and comfort: a highly present 43 mm Masterpiece

The round case measures 43 mm in diameter and combines satin-brushed and polished surfaces. Its thickness is substantial, around 16 mm on documented references, giving the watch considerably more presence than a conventional dress watch. The diameter is largely explained by the space required for the large seconds display and the off-centred hours-and-minutes subdial. The front crystal is domed sapphire with anti-reflective coating on both surfaces. The 43 mm format should be considered part of the mechanical spectacle rather than an attempt to create a slim watch. On an average wrist, the watch occupies significant space and its height remains noticeable beneath a cuff. Exact lug-to-lug length is not communicated in the principal period specifications, making an actual wrist test particularly useful for someone accustomed to watches smaller than 40 mm.

The screwed caseback contains a large sapphire crystal through which the automatic calibre, rotor and bridge decoration can be observed. Water resistance is limited to 50 metres, or 5 ATM. This level suits normal daily wear and accidental contact with water but clearly does not turn the Mysterious Second into a sporting or aquatic watch. The 50-metre water-resistance rating is more consistent with a contemporary mechanical showpiece than a tool watch. Given the age of the earliest examples, a pressure test is advisable before repeated exposure to moisture. Sapphire provides effective protection against ordinary scratches, but the numerous polished case surfaces can mark more readily and excessive refinishing risks altering the transitions between polished and satin-brushed areas.

Classical references are generally paired with black or brown crocodile straps, leather lining and either a folding clasp or pin buckle depending on version. This reinforces the dressier side of the watch and visually balances its large diameter. Black versions naturally tend to use dark straps, while stainless-steel configurations with lighter displays are often paired with brown. A comparatively supple strap is preferable for stabilising the thick case without unnecessarily adding weight. The watch is not built around an integrated bracelet and can therefore be customised relatively easily provided the correct lug width is respected. On the pre-owned market, the condition of the original organic strap matters less than that of the case and movement because a leather strap is fundamentally a consumable component. Retaining the original Maurice Lacroix buckle nevertheless adds interest to a complete example.

ML215 movement: 18,000 vibrations and the mechanics of illusion

Calibre ML215 is an automatic mechanical movement developed to implement the unusual display of the Mysterious Second. It contains 48 jewels, operates at the relatively slow frequency of 18,000 vibrations per hour, or 2.5 Hz, and provides approximately 50 hours of power reserve. The lower frequency compared with the 4 Hz common in contemporary Swiss watchmaking contributes to the particular visual animation of the seconds indication. The ML215 is designed primarily to serve the architecture of the mysterious display rather than pursue a high operating frequency. It also drives the off-centred hours and minutes at 2 o’clock. The movement contains more than two hundred components and collection documentation notably mentions sandblasted bridges, worked edges and a rotor decorated with a Grand Colimaçon-style pattern or Geneva stripes depending on execution.

Its 50-hour reserve is sufficient to leave the watch unworn for a full day without stopping, although it is shorter than contemporary movements regularly exceeding 70 hours. Automatic winding nevertheless eliminates the need to use the crown every day when the watch is regularly worn. Detailed official accuracy according to current standards is not communicated and the Mysterious Second is not presented as a certified chronometer. On a pre-owned example, the condition of the display mechanism matters more than a theoretical comparison of a few seconds of daily rate variation. The complication adds specific components whose correct adjustment determines the fluidity of the spectacle. A hesitating hand, irregular transition between sequences or unusual noise therefore deserves inspection by a watchmaker familiar with Maurice Lacroix movements from this generation.

Calibre finishing varies between different executions. Early lighter versions favour rhodium plating while darker models notably use ruthenium or black treatments. The movement remains visible both from the partially open dial and through the sapphire caseback, providing two very different perspectives on the mechanics. This dual visibility makes the ML215 an aesthetic component as important as either the case or dial. For the buyer, it also means that the cosmetic condition of the movement deserves genuine inspection: scratches on the bridges, damaged screws or signs of intervention may be immediately visible. Servicing will naturally be more specialised and potentially more expensive than maintenance of a standard automatic movement, something that should be included in the budget for a watch now primarily found on the pre-owned market.

Chronological milestones and main models (2013–2025)

(2013) Maurice Lacroix Masterpiece Seconde Mystérieuse Steel Rhodium First Light Series:

The first light-coloured interpretation is one of the two references that introduce the concept at Baselworld 2013. The Maurice Lacroix Masterpiece Seconde Mystérieuse MP6558-SS001-090 has a 43 mm stainless-steel case with satin-brushed and polished surfaces, domed anti-reflective sapphire and a screwed caseback largely occupied by a display crystal. Water resistance reaches 50 metres. The partially skeletonised dial highlights a pale seconds display with a blue hand, while hours and minutes appear in a subdial positioned around 2 o’clock. The bridges of automatic calibre ML215 receive a rhodium-plated presentation that strengthens the contrast with the blue elements. The movement operates at 18,000 vibrations per hour, contains 48 jewels and provides approximately 50 hours of power reserve. This version is produced as a limited series of 125 pieces and is generally associated with a brown or dark crocodile strap.

(2013) Maurice Lacroix Masterpiece Seconde Mystérieuse Black PVD Ruthenium First Dark Series:

The second launch configuration adopts a substantially more technical and monochromatic aesthetic. The Maurice Lacroix Masterpiece Seconde Mystérieuse MP6558-PVB01-090 retains a 43 mm stainless-steel case but receives a black PVD coating that radically changes its wrist presence. The domed sapphire remains anti-reflective and the sapphire back still allows the movement to be observed. Its partially skeletonised dial uses black and grey shades with ruthenium-finished bridges and a contrasting large seconds display. Automatic calibre ML215 retains its 48 jewels, 18,000 vibrations per hour frequency and 50-hour autonomy. Water resistance remains 50 metres. This version is also limited to 125 examples, bringing total production of the two inaugural series to 250 watches. Its black crocodile strap and dark case treatment make it visually the more discreet of the two original versions despite the substantial physical presence of the complication.

(2013) Maurice Lacroix Masterpiece Seconde Mystérieuse Only Watch Unique ADLC Piece:

For the Only Watch 2013 charity auction, Maurice Lacroix creates a unique and even darker execution. The Maurice Lacroix Masterpiece Seconde Mystérieuse MP6558 receives an ADLC treatment applied to the stainless-steel case as well as several movement, dial, crown and buckle components. Diameter remains 43 mm and water resistance 50 metres. Automatic calibre ML215 still operates at 18,000 vibrations per hour and provides approximately 50 hours of reserve. Its sapphire caseback reveals a rotor carrying a specific Only Watch 2013 inscription and identifying the watch as the unique 1/1 piece. A black crocodile strap completes the presentation. The large mysterious seconds display follows the same operating principle, but the almost entirely black palette further emphasises the experimental nature of the construction. This is not a production reference but a watch specifically created for the Monaco auction benefiting research into Duchenne muscular dystrophy.

(2014) Maurice Lacroix Masterpiece Mysterious Seconds Light New 250-Piece Series:

After the two inaugural series, Maurice Lacroix develops a lighter version whose production increases to 250 examples. The Maurice Lacroix Masterpiece Mysterious Seconds MP6558-SS001-094-2 retains stainless steel, the 43 mm diameter, domed anti-reflective sapphire, transparent caseback and 50 metres of water resistance. Its seconds display uses a light background creating strong contrast with the markings and skeletonised dial architecture. Hours and minutes remain off-centred at 2 o’clock and the movement continues to be the automatic ML215. It contains 48 jewels, operates at 18,000 vibrations per hour and provides 50 hours of power reserve. A brown crocodile strap with folding clasp strengthens the more classical character of this configuration. The Mysterious Seconds receives the Red Dot Design Award Best of the Best in 2014, an important distinction for a watch whose originality lies precisely in visually reorganising such an elementary horological indication.

(2014) Maurice Lacroix Masterpiece Mysterious Seconds Dark New Black 250-Piece Series:

The darker variation accompanies the lighter model with the same architecture and production again limited to 250 pieces. The Maurice Lacroix Masterpiece Mysterious Seconds MP6558-SS001-095-1 uses a 43 mm stainless-steel case but gives the dial and large seconds display substantially darker tones. Its black strap reinforces this monochromatic presentation. Sapphire protects the partially skeletonised dial and the caseback reveals calibre ML215. Frequency remains 18,000 vibrations per hour, power reserve 50 hours and water resistance 50 metres. Hours and minutes are still displayed on the small subdial around 2 o’clock, while the mysterious indication dominates the lower half. The reference therefore does not change the complication itself but gives the design a more contemporary and visually discreet personality than the silver-toned execution, particularly when the watch is viewed from a distance.

(2016) Maurice Lacroix Masterpiece Mysterious Seconds Revelation Black Partial Revelation of the Mechanism:

In 2016, Maurice Lacroix revisits the concept with an evolution called Revelation, intended to expose more of the construction without completely eliminating the mysterious effect. The Maurice Lacroix Masterpiece Mysterious Seconds Revelation MP6558-PVB01-092-1 adopts a 43 mm black-PVD case, domed anti-reflective sapphire and an even darker dial-and-movement architecture. The seconds mechanism remains the principal attraction, with its reading alternating between horizontal and vertical axes every fifteen seconds. Automatic calibre ML215 contains 48 jewels, operates at 18,000 vibrations per hour and has 50 hours of power reserve. Water resistance remains fixed at 50 metres. Black bridges, sandblasted finishes and the decorated rotor strengthen the mechanical appearance of the complete watch. Its black crocodile strap completes a piece more focused on a technical aesthetic than on the classical elegance of certain light stainless-steel executions.

(2016) Maurice Lacroix Masterpiece Mysterious Seconds Revelation Steel Light Revelation Version:

The stainless-steel version of the same development makes the contrasts between different mechanical components easier to observe. The Maurice Lacroix Masterpiece Mysterious Seconds Revelation MP6558-SS001-096-1 has a 43 mm stainless-steel case, domed anti-reflective sapphire and transparent caseback. Its lighter dial highlights the seconds display, movement bridges and small off-centred hours-and-minutes indication more strongly. Automatic calibre ML215 retains 48 jewels, 18,000 vibrations per hour and approximately 50 hours of reserve. Water resistance remains 5 ATM. The watch is generally paired with a brown crocodile strap and stainless-steel folding clasp. This evolution therefore does not alter the fundamental characteristics of the Mysterious Second but provides another way to experience its construction. After this period, the model progressively disappears from the regular catalogue and becomes primarily a watch sought on the pre-owned market rather than a collection continuously renewed through 2025.

Choosing the right version: light, dark, first series or Revelation

For someone seeking the version historically closest to the launch, the 2013 references are the most interesting. They correspond to the two original 125-piece series and present the complication exactly in the form in which it was introduced at Baselworld. The MP6558-SS001-090 is probably the clearest reference for visually discovering how the mysterious seconds operates. Its lighter bridges and blue hands make the different mechanical elements easier to distinguish. The black PVD model is both more spectacular and more discreet, although wear can also become more noticeable on an aged surface coating.

The 250-piece versions are generally easier to encounter on the pre-owned market and retain the same ML215 calibre. Everyday functional differences between a first series and a subsequent generation are therefore relatively modest. The choice can reasonably be based on condition, colour and service history rather than year alone. A complete watch with box and papers can have additional collector appeal, but a properly serviced and well-preserved example is often a more sensible purchase than a complete watch that has never received appropriate maintenance.

The 43 mm diameter and thickness close to 16 mm need to be taken seriously. The watch has genuine physical presence and its asymmetrical architecture makes it appear even larger visually. Trying the watch on is strongly recommended for someone accustomed to watches in the 38 to 40 mm range. A leather strap can be adjusted to stabilise the case properly but cannot completely disguise its height. Beneath a tightly fitted cuff, the Mysterious Second will be considerably less discreet than a more conventional three-hand Masterpiece.

The ML215 and especially its specific display mechanism deserve more attention than a standard automatic movement before purchase. The watch should be observed for a complete minute to verify the regularity of all four fifteen-second sequences, hand rotation and transitions between axes. The mysterious seconds should be checked over a complete minute rather than observed for only a few seconds. A documented service history is an advantage because specialised work can be more demanding than maintenance of a common calibre. The condition of the visible movement surfaces should also be checked because they form a direct part of the watch’s appearance.

Finally, the watch should be considered a mechanical conversation piece or collector’s watch rather than an all-purpose tool watch. Its 50 metres of water resistance, leather strap and substantial thickness naturally direct its use towards the office, social occasions and a multi-watch rotation. Its principal appeal lies in the visual and mechanical experience of the complication rather than everyday versatility. For regular wear, a stainless-steel version may be cosmetically easier to maintain than an older PVD or ADLC execution. Other customers’ opinions are essential.

Conclusion

The Maurice Lacroix Masterpiece Mysterious Second is aimed at enthusiasts who regard the display of time as a field for mechanical experimentation as much as a practical reading tool. Its oversized seconds indication, off-centred hours-and-minutes display and partially skeletonised dial make a watch immediately recognisable and very different from a conventional three-hander. Calibre ML215 brings mechanics specifically developed around this display, with 48 jewels, 50 hours of power reserve and a deliberately moderate frequency of 2.5 Hz. The first 2013 series are most directly connected with the launch, the 2014 versions broaden production and the 2016 Revelation models expose more of the mechanics. Its 43 mm diameter, considerable thickness and 50 metres of water resistance nevertheless limit versatility.

To compare comfort, accuracy, reliability of the complication and the genuine long-term pleasure of this unusual display, Dialicious customer reviews provide a particularly useful complement.

(Updated September 2026)