Sinn EZM1

Sinn is a German watch company founded by Helmut Sinn which he later sold to Lothar Schmidt, formerly of IWC. Over the years Sinn developed a reputation for producing high quality tool (or as they like to call them, instrument) watches at very reasonable prices. However, they were virtually unknown outside of Europe, because you could only order them direct from the factory in Frankfurt. But with the advent of watch forums where lucky individuals posted pictures of their Sinns coupled with the rising popularity of online shopping the word was out. By the time I first saw the EZM1 there was already an authorized dealer in the United States. It was marketed as a "tactical watch" and indeed it was developed for use by German law enforcement units. EZM is an abbreviation for Einsatzzeitmesser, which roughly translates to "Operational Mission Timer." You can read more about the EZM1's history here in an article by Bob of MWR.

I was intrigued by some of the EZM1's uncommon features: The crown and pushers on the left side of the case; a count-down bezel insert; a "dead" dial; and finally, the lack of any subdials even though it's a chronograph.

But let's start with the case which is made of titanium instead of steel. Titanium has some advantages over stainless steel. It won't rust and is highly resistant to corrosion, it's hypoallergenic, and is lighter than steel but just as strong. Some disadvantages are that titanium can scratch easier than steel unless its surface is coated or specially hardened. Another aspect of titanium is that over time two pieces of titanium in constant contact with each other can fuse together to form one piece of titanium.

The surface of the case is bead-blasted to a satin finish to prevent any unwanted reflections. The EZM1 measures approximately 16.5 mm high from the caseback to the top of the domed crystal. This is unequivocally the tallest watch I have ever owned. However, the wrist presence is akin to that of a Rolex Sea-Dweller since the diameter is about 40 mm. There's a copper sulfate (CuSO₄) capsule embedded in the 1 o'clock lug.

According to Sinn the capsule should absorb any moisture that has gotten into the case. The capsule changes color from near white when it's completely dry to dark blue when it's completely saturated.

The crown and pushers are located on the left side of the case to reduce the possibility of snagging the watch on something underwater. Granted you'll have to be wearing the watch on your left wrist to take advantage of this feature. The signed crown screws down with internal threads, while the chronograph pushers are the non-screwdown variety.

The bezel is bidirectional and solidly clicks into place. I haven't taken the bezel off, but it feels and sounds like a click ball instead of a spring is used to turn it. The anodized aluminum insert features a 60-minute countdown scheme with a luminous triangle insert at 60.

The watch has a high domed sapphire crystal with an anti-reflective coating on the inside surface. The EZM1 is water resistant to 30 bar or about 300 meters/1000 feet.


The EZM1 has one of the best designed dials since the Omega Speedmaster. It's a very dark matte black with luminous rectangular hour markers. There's a double marker at the 12 o'clock. A date window appears offset at the 3:30 position. This prevents the window from "eating" any of the luminous hour markers and helps keep the symmetry of the dial intact to an extent. The luminous material used in the Ar-dialed EZM1s is superluminova and it glows like a torch.

All of the writing on the dial and the numbers on the date wheel are printed in red. The subdued color aids in legibility. When you need to glance at the time, the distractions from the dial text and date window are minimized. The circle Ar denotes the use of Argon gas inside the watch case to prevent moisture from forming. This is a Sinn innovation along with the CuSO₄ capsule (the more cynical might call them gimmicks). All I know is that if I need both replaced, only the Sinn factory can refill the Argon and replace the capsule.

(Earlier EZM1 models featured circle 3H dials denoting the use of tritium luminous. I've heard that if you send your 3H-dialed EZM1 to Sinn for servicing they will replace the dial and hands with the superluminova types, no ifs, ands, or buts. Supposedly it's a safety issue.)

The luminous on the hands doesn't extend the full length of the shaft. This gives them a floating appearance. The hour and minute hands are frameless and are "pencil-shaped" for lack of a better term. The minute hand sports a long and thin needle-like tip. The other two hands are only used when the chronograph is activated. There's the chronograph seconds sweep and the airplane-shaped central minute counter (in lieu of a minute counter subdial). The latter is a hallmark of the Lemania 5100 automatic chronograph movement which beats inside the EZM1.

The Lemania 5100 features a day/date window, a 24-hour counter subdial, a constant seconds subdial, a 12-hour counter subdial, and a central minute counter with a central chronograph sweep. As you've noticed, the EZM1 doesn't use most of these features. Instead, the designers focused on dial legibility and being able to tell the time at-a-glance, which meant displaying the time without any "unnecessary distractions." The lack of a constant seconds subdial in particular takes some getting use to. The watch has a dead dial in the sense that you don't see any of the hands moving (if the chrono is not engaged). Sometimes I have to bring the watch up to my ear to hear the ticking just to make sure that it's still running.

The Lemania 5100 is now officially discontinued by the Swatch Group. It was used extensively in military watches by Tutima, Porche Design, Arctos, and others because of desirable features such as the central minute counter and its proven ruggedness. However, the movement is not without its quirks. There have been problems with a low power reserve in watches using the L5100 and the EZM1 is no exception. In the EZM1's case whether this has to do with lubrication issues (Not enough? Too much?), the inefficiency of the unidirectional winding rotor, or an artifact of flipping the movement 180 degrees to fit in the case is still unclear.

Other reported issues with the L5100 in general and the EZM1 in particular is that the chronograph hands don't reset to zero every time. This can be rectified by clicking the reset pusher again or initially pushing it with sufficient force.

The last issue with the EZM1 doesn't involve the movement, but rather the bezel insert. The insert is actually glued onto the bezel. In hot weather, the adhesive has been known to weaken resulting in the insert falling off. An embarrassing and ignominious problem for such a tough and "tactical" watch. Sinn could have avoided this if the insert snapped onto the bezel like a Rolex insert.

The quirks and problems aside, the EZM1 is a looker. I found that it sits most comfortably on my wrist when I wear it on a cloth strap. I currently wear my EZM1 on an olive milstrap. I tried it on the solid end link titanium bracelet and the Sinn stitched rubber strap, but they just don't hold the watch tight enough for me.

The EZM1 was discontinued about 2 years ago (late 2004) shortly after the Lemania 5100 was discontinued. There were only about 3000 produced which makes it a limited production model (as opposed to a limited edition). I arrived at that number since the serial number on my watch is in the high 2900s. I ordered mine right when they were discontinued and not too long before the last EZM1 left the Sinn factory in Frankfurt. So if you want one, you're going to have to look on the secondary market.