Welcome to Watches You Should Know, a biweekly column highlighting little-known watches with interesting backstories and unexpected influence. This week: the Sinn EZM 1.

Almost no other watch brand owns the image of the purpose-built, ultra-tough, German-made tool watch quite like Sinn.

This tool watch ethos means stripping a design down to its essential elements for a rugged, utilitarian focus — and somehow, this honed simplicity can end up looking beautiful. This is precisely what Sinn as a brand means to many people, and no watch better represents that philosophy than the EZM 1.

Introduced in 1997, one look at the EZM 1 tells you it’s a bit quirky, and closer inspection reveals several unusual features. Thanks to its sober design language, one tends to assume these quirks aren’t merely aesthetically driven, even without necessarily understanding their purpose. And one would be right — special dehumidifying technology, an extensively modified movement, extreme temperature resistance and a titanium case are just some of what makes this watch unique.

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Einsatzzeitmesser (EZM) is “mission timer” in German, and the EZM 1 was in fact designed specifically for use by a special tactical unit of the German customs service. Aside from its functional, instrument-like appearance, the first thing most people will probably notice about the EZM 1 is that its crown is oritned on the left side of the case and flanked by chronograph pushers. But those pushers aren’t joined by the typical set of subdials one tends to associate with a chronograph. So what’s going on?

This is indeed a chronograph, but both its needle-like seconds hand and minute hand (with the airplane-shaped tip) are centrally mounted, leaving the dial as clean as a plain old, time-only three-hander. In other words, you can measure up to 60 minutes on the chronograph, but there is no indication for the main time’s seconds. This lefthand positioning (“destro”) prevents the discomfort of a crown digging into your wrist, and it’s just as easy to operate as the traditional orientation.

Powering the watch is the famed Lemania 5100, and turning it into a central chrono did undoubtedly take some significant tweaking by Sinn. The 5100 is an appropriately robust automatic movement without the pretense of pretty decoration, and when making full use of all its functions, it offers no fewer than seven hands, plus day and date wheels. Sinn did keep the date display, but chose to position it at roughly 3:45. The Lemania 5100 isn’t made anymore, so when Sinn brought the watch back in the larger-cased EZM 1.1 in 2017, it used a modified ETA/Valjoux 7750.

There’s even more that makes the Sinn EZM 1 stand out. Sinn uses a range of technologies not often found elsewhere to improve its watches’ longevity. That circled “Ar” on the dial indicates an Ar-Dehumidifying Technology system of the brand’s own development. It comprises three elements including special seals and an argon (“Ar”) gas injection to replace oxygen and any moisture the case might contain. Finally, a drying capsule (visible through a sapphire window at one of the lugs) turns blue over time to indicate that it has absorbed moisture and needs to be replaced. These and similar technologies continue to be used in many Sinn watches today.

Add to all the aforementioned toughness 300m of water resistance and temperature tolerance of –20°C to +70°C and you’ve got one badass, technical watch. The EZM measures only 40mm wide, but chronograph movements tend to be bulky, and this leads to a case that’s about 16mm thick. To offset that potential heft, the case is crafted entirely in lightweight titanium and weighs a mere 61g without a strap. Its matte, bead-blasted treatment is devoid of any shine — just one more element that communicates a get-on-with-it attitude.

The original EZM 1’s production ended with that of the Lemania 5100 movement. Some 20 years after its release, in 2017, Sinn introduced a successor watch, the EZM 1.1. A limited edition of 500, the 1.1 is larger than the original at 43mm wide and runs on a modified ETA/Valjoux 7750 movement, and it’s made of steel (rather than titanium) that’s been treated to the brand’s tegimented hardening process.

No-nonsense, unique and totally badass, the original Sinn EZM 1 remains an unusual and compelling modern watch that even vintage collectors are drawn to.

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