From the Lemania 5100 to the Sinn SZ01 Movement

Why the Lemania 5100 Mattered

The Lemania 5100, produced from 1974 until 2002, was never a conventionally beautiful movement. Lemania built it from stamped steel and Delrin, a low-friction engineering plastic, with the explicit goal of competing against inexpensive chronographs from Seiko and other Japanese makers. It was designed to be cheap to assemble and cheap to service. Its reputation rests instead on two things: toughness, and a display that made elapsed time unusually legible.

A Four-Handed Dial

A typical Lemania 5100 configuration places both chronograph seconds and chronograph minutes on the central axis, giving watches that use it a distinctive four-handed look. The long chronograph-seconds hand circles once per minute, while a separate long central hand indicates elapsed minutes over a 60-minute scale. A sub-dial at 6 o'clock records up to 12 elapsed hours, small seconds sit at 9 o'clock, a 24-hour indication occupies 12 o'clock, and day and date windows sit at 3 o'clock. The movement runs at 28,800 vibrations per hour, uses 17 jewels, and offers a 48-hour power reserve.

The central minute hand is the detail that matters. Instead of locating elapsed minutes inside a small register, the wearer reads a long hand against a full-diameter scale — no need to identify a sub-dial, resolve its small numerals, or distinguish its hand from the running-seconds and hour-totaliser hands nearby. The dial reads like an instrument panel rather than a traditional three-register chronograph.

The 140 S in Orbit

Sinn's use of the movement made this proposition concrete. German physicist and astronaut Reinhard Furrer wore a Sinn 140 S, powered by the Lemania 5100, during the 1985 Spacelab D1 mission — demonstrating that an automatic watch could continue to wind itself in a weightless environment. Seven years later, astronaut Klaus-Dietrich Flade took a 142 S on the Mir-92 mission, extending the series' spaceflight record.

The 140 and 142 therefore became important not merely as space watches but as early expressions of a Sinn design language in which the mechanism determines the interface. The 5100's architecture dictated the watch's most recognisable visual feature, and Sinn embraced that rather than disguising it.

The EZM 1 Distilled the Doctrine

The purest expression arrived in 1997. Sinn developed the EZM 1 in direct collaboration with the ZUZ — the Zentrale Unterstützungsgruppe Zoll, or Central Customs Support Group, a special unit of the German Customs Investigation Bureau comparable to a special police commando. The unit's number one requirement, Sinn records, was outstanding readability at a glance in time-critical situations. EZM itself stands for Einsatzzeitmesser, German for mission timer.

The result was a titanium chronograph with the crown and pushers moved to the left side of the case, where they could not press into the back of the hand or snag during an operation. And because the Lemania 5100 already carried minutes and seconds centrally, Sinn deleted every sub-dial. The EZM 1 is perhaps the most unusual 5100-powered watch ever made: no sub-dials at all, just two central chronograph hands against a clean scale.

A ZUZ-marked dial went to the unit; a civilian version, marked 3H, accompanied it.

The 7750 Transition Years

Lemania ended 5100 production in 2002. Remaining supplies carried the EZM 1 until 2004, when Sinn discontinued the model.

The obvious industrial replacement was the ETA/Valjoux 7750, the dominant automatic chronograph calibre of the modern Swiss industry. The 7750 is a cam-actuated movement: a shaped cam, rather than the more elaborate column wheel, coordinates the start, stop, and reset functions, which has helped make it robust, widely understood, and comparatively practical to service. Its default display is equally familiar: central chronograph seconds, a 30-minute counter at 12 o'clock, running seconds at 9 o'clock, and a 12-hour counter at 6 o'clock, with day and date at 3.

What the Standard Layout Loses

That arrangement works well, which is precisely why it became a standard — but it solves the display problem differently. The elapsed-minute totaliser shrinks to a small sub-dial, usually covering only 30 minutes, so the wearer must shift attention from the central hands to a compact register with its own scale. Timing beyond 30 minutes requires reading a second totaliser, or stopping and restarting the measurement, and the one-glance, one-answer quality of the 5100 display disappears.

For a motorsport-inspired or general-purpose chronograph, none of this is fatal. For a mission timer built around the premise that elapsed minutes are the primary readout, it was a fundamental regression.

Even the 5100's Own Successor Abandoned It

The clearest evidence that the industry considered the central minute counter expendable came from inside ETA itself. In 2008, at Tissot's request, ETA created the C01.211, a low-cost chronograph derived directly from the Lemania 5100's design. ETA reduced the jewel count to 15, slowed the beat rate, and moved the minute counter from the centre to a sub-dial at 12 o'clock.

In other words, when industrial logic dictated a cheaper movement, the central minute hand was the first thing sacrificed. Sinn went the other direction.

The SZ01 as Sinn's Answer

The Sinn SZ01 movement is a chronograph calibre developed in house on the Valjoux 7750 base, with one defining purpose: restore the central elapsed-minute display that the Lemania 5100 had made possible.

The SZ01 carries a centre-mounted, jumping 60-minute stop hand alongside the central chronograph-seconds hand. Jumping means the minute hand advances in distinct one-minute steps rather than creeping continuously, so each reading is stable and unambiguous — the hand lands on the minute marker instead of hovering between markers. Sinn identifies two legibility gains over a standard layout: a full 60 minutes, rather than the usual 30, are counted in one sweep of the hand, and the minute scale spans the entire diameter of the dial.

One clarification matters for first-time buyers: in-house-developed here does not mean a clean-sheet manufacture calibre. The underlying architecture is the proven 7750. What Sinn developed is the substantial modification that transforms that architecture's display into something a stock 7750 cannot produce. The distinction is exactly the point — the added value lives in the interface, not in exclusivity for its own sake.

The movement arrived in 2017 in the EZM 1.1, a 500-piece limited edition marking 20 years of the mission timer line. The watch shows how completely the doctrine shapes the hardware: the SZ01 runs at 28,800 vibrations per hour with 28 jewels and a self-winding mechanism, and includes a seconds stop function for precise setting. Sinn hardened the bead-blasted stainless steel case with TEGIMENT, its surface-hardening process, replacing the original's titanium and growing the case from 40mm to 43mm. The crown and push-pieces moved to the left side, now with Sinn's D3-System, alongside a captive, bidirectional pilot's bezel with minute ratcheting and a luminous key mark usable to record cumulative time alongside the chronograph. All dial markings not relevant to the mission are muted in red, and Ar-Dehumidifying Technology, functional reliability from –45°C to +80°C, 20-bar pressure resistance, and resistance to low pressure round out the mission-timer specification.

A black follow-up, the EZM 1.1 S, launched in 2022 at a reported price around €4,980.

The SZ01 also powers the modern 140 St S, which pairs the space-chronograph case lineage with the centre-mounted jumping 60-minute hand. The link to Furrer's 1985 watch is therefore unusually direct: not the same calibre, but the same timing priority, delivered through a different mechanical route.

Movement Comparison

Put the three calibres side by side and the display hierarchy tells the story. The Lemania 5100 (1974–2002) gave both chronograph minutes and seconds a central hand, built from stamped steel and Delrin with 17 jewels and a 48-hour reserve — an instrument-panel readout rather than a conventional three-register layout. It powered the Sinn 140 S and 142 series and the original EZM 1, but it has been out of production since 2002, and its stamped, plastic-heavy construction means parts and expertise are increasingly scarce outside a shrinking pool of specialist watchmakers.

The standard ETA/Valjoux 7750, introduced in 1973/74, is cam-actuated rather than column-wheel-controlled and pushes elapsed minutes into a 30-minute sub-dial at 12 o'clock. That conventional three-register display is exactly what makes the 7750 ubiquitous: it is robust, broadly familiar to watchmakers worldwide, and easy to source parts for — but it never offered the 5100's central-minute readout.

The Sinn SZ01, introduced in 2017 on the 7750 base, restores that central jumping 60-minute counter while keeping the base movement's serviceability. It carries 28 jewels in the EZM 1.1 and powers that watch alongside the EZM 1.1 S and the modern 140 St S. Because the 7750 base is broadly familiar, routine service is accessible — but the Sinn-specific modifications argue for Sinn or an authorised service centre for anything beyond the basics.

One buying implication follows directly: 7750-based does not mean equivalent. A shopper who sees the base calibre named and assumes the SZ01 is visually or functionally interchangeable with a normal three-register chronograph will miss the entire engineering intervention.

Related guideChronographs →

Sinn's Engineering Culture

Sinn's own account of its mission timers names the governing principle plainly: form follows function, with requirements defined by professional users and the conditions they operate in. The SZ01 is that principle applied to a supply problem. The Lemania 5100 disappeared; Sinn did not pretend the SZ01 was the same calibre, and it did not reproduce the 5100 as a historical exercise. It identified the feature worth retaining — readable elapsed minutes at the dial centre — and rebuilt it on a serviceable modern base.

Three habits emerge from the lineage. Interface before nostalgia: the SZ01 preserves the 5100's most useful user-facing trait, not every mechanical detail of the older calibre. Modification as a design tool: Sinn starts from a proven industrial movement and changes it where the application demands a different result. And legibility as engineering: the central minute counter is not decoration, it changes how quickly a timed interval can be read.

That is why the Sinn SZ01 movement matters beyond a single model. It is a case study in what a proprietary calibre can mean when the goal is a better match between mechanical architecture and operational use, rather than marketing separation from third-party suppliers.

Summary

The Lemania 5100 gave Sinn an unusually direct chronograph display: elapsed minutes and seconds both read from the centre, with minutes given the scale and prominence that real timing tasks demand. When 5100 production ended in 2002, a standard Valjoux 7750 could supply reliable automatic chronograph mechanics but not the same display hierarchy, and even ETA's own 5100-derived successor abandoned the central minute hand.

Sinn's answer was the SZ01, a 7750-based movement modified in house to restore a central, jumping 60-minute counter. From the 140 S in orbit to the EZM 1, the EZM 1.1, and the modern 140 St S, the doctrine has remained constant: protect the function that matters, even when the component that originally enabled it is gone. Take the seven-question quiz to find watches that are genuinely built for the way you actually tell time.