A deep look at the Sinn U2 – Review

Today, I decided to present to you the watch that is closest to my heart because all my family, my parents-in-law and my wife have contributed to surprise me for my 40 years by organizing a weekend at Sinn in Frankfurt to get this Sinn U2.

Let’s start with the history of the Sinn brand

In 1961, Helmut Sinn, an instructor for blind fight and former WWII pilot, founds the company « Helmut Sinn Spezialuhren » in Frankfurt am Main. The company’s core business is the manufacture of navigation clocks and pilot chronographs.

Helmut Sinn (1916-2018) _ credit http://www.sinn.de

In 1994, the certified Engineer Lothar Schmidt acquires the company and initiates a major strategic reorganization to lead the company into the future and enhance its technological expertise. The company is renamed “Sinn Spezialuhren GmbH”.

In 2017, Sinn moved from their historical location to Frankfurt-Sossenheim in an approximately 7.000 square meters new property with the possibility to buy watches directly at their headquarters (what I did with the Sinn U2).

Sinn Headquarters in Frankfurt Sossenhein (Credit http://www.sinn.de)

Some sad news in 2018 as Helmut Sinn has died at the age of 101. Helmut Sinn was recognised as an extraordinary and strong willed personality.

Since its creation in 1961 until today, Sinn Spezialuhren has been one of the leaders of technical innovations in the world of watchmaking. Indeed, Sinn Spezialuhren has developed technologies such as:

  • Ar-Dehumidifying Technology: it prevents the crystal from fogging up even when faced with sudden temperature changes and effectively retards the aging process of the components in the watch, thereby extending the functional life of the watch.
  • Development of HYDRO Technology: it guarantees absolute freedom from fogging, pressure resistance at every accessible diving depth and optimal readability under water at any angle.
  • The DIAPAL Technology: it features a special combination of materials that requires no lubrication, thereby ensuring long-term precision of the movement.
  • TEGIMENT Technology: The stainless steel watch case hardened using the pioneering technology effectively protects against scratching.
  • And many other innovations…

Moreover in 1997, Sinn Spezialuhren introduces the EZM1 and EZM2 mission timers:

Known as a maker of special timepieces, Sinn once again proves its competence with the development of two mission timers known as the EZM1 and EZM2. These timepieces are designed for use in missions by special police forces and the GSG 9 (Border Protection Group 9 of Federal Police). The mission timers focus on the absolute essentials: optimal readability and perfect measurement of time. In the following years, additional mission timers were developed for special, professional user profiles.

Germany’s commando frogman force KSM (Kommando Spezialkräfte der Marine)  are wearing Sinn watches (Credit http://www.sinn.de)

Since then, Sinn Spezialuhren has been creating many watches for professionals with the EZM (Einsatzzeitmesser) range that can be translated literally by Mission Timer. These watches have been specially developed for a particular purpose. They always offer excellent readability. This means: the form is always dictated by the function and handling requirements. Like for example, the EZM7 developed for the fire brigade with its colour-code bezel making easy for people using breathing protection apparatus to set and read off the relevant duration (CSA and LPA).

Sinn EZM7 developed for the fire Brigade (credit http://www.tokei.biz)

Now, we will focus on the watch itself, the Sinn U2 (EZM5): The Mission Timer for divers made of German Submarine Steel.

The Sinn U2 is a professional mission timer made of genuine German Submarine Steel which offers an extreme seawater resistance and high level of non-magnetic properties as per DIN8309. According to this norm, a watch must resist exposition to a direct current magnetic field of 4800 A/m (Ampere per meter).

The German Submarine manufacturer ThyssenKrupp Marine Systems provides a small amount of their overall steel production to Sinn.

Sinn is also using as special oil (Sinn 66-228) which is a high grade oil specially developed for Sinn; its properties allow the watch to run accurately from -45°C to +80°C. EDR Seals are there to prevent fog on the dial when diving. This seals are chemical resistant and offer more non-permeability than a conventional seals.

The Sinn U2 is also equipped with the Ar-Dehumidifying Technology with 3 drying capsules inside the watch. One is visible at 6 o’clock and the two other ones are inside the case. Ar-Dehumidifying technology solves a basic problem of mechanical watches: the aging of oils due to moisture in the air contained inside the watch.

The watch is filled with a protective gas that creates an ideal climate for the Ar Technology. Moreover, 3 drying capsules filled with copper sulphate are inside the watch which turn from white to blue as an indicator of the drying capsule’s level of saturation.

The copper sulfate capsule www.dvkphotography.com

This is some of the technical qualities developed by Sinn for this watch which proves that Sinn Spezialuhren produces timepieces for professionals and meant to be used in the more critical situations.

Let’s have a closer look at the watch

The case diameter is 44mm with a lugs to lugs distance of 52mm. The case thickness is about 15.5mm and the weight of the watch without strap is 114 grams + 105 grams for the bracelet with all the links.

It’s really a watch that we feel and see on the wrist!

The case is bead blasted with drilled lugs which is an appreciate feature on a tool watch. A great screw down crown signed with the S of Sinn is placed at 4 o’clock in order to avoid disturbance while moving the wrist.

Screw down crown with Sinn initials www.dvkphotography.com

The watch is 2000 Meters water resistant. Yes, 2000 METERS or 200ATM which is quite incredible and I hope I will never experience that personally. The watch is certified by the DNV GL who provides technical testing and certification. DNV GL has been testing Sinn watches since 2005. The tests are repeated at regular intervals on all of their watches in order to document the consistency of the overall quality.

Moreover, DNV GL certifies that the watch complies with the European diving equipment standards (EN250 and EN14143). The experts at Germanischer Lloyd thus adapted the standards appropriately and defined two series of tests. In the first of the two, they put the timepieces in a test cabinet for three hours at minus 20°C, then for three more hours at 50°C. The timepieces were subsequently checked for accuracy and functional reliability at both temperatures. In a second test, the watches had to withstand three hours at minus 30°C and 3 hours at 70°C with 95% humidity.

Sinn Spezialuhren is the first company in the watch industry to have its diving watches certified by Germanischer Lloyd (Now DNV GL) of Hamburg for compliance with European standards for diving equipment. (Credit http://www.sinn.de)

The movement is an ETA 2893-2 with 21 jewels and 28.800 semi-oscillations per hour (4Hz) and with of course, a stop second function. The ETA Manufactory is based in Grenchen (Switzerland) and belongs to the Swatch Group (Breguet, Blancpain, Glashütte Original, Omega, Tissot, Hamilton, Swatch, etc.) and are producing high quality movements for their own brands but also for other brands like Sinn.

Regarding the precision of my Sinn U2, it is really good as it runs with +2 seconds per day! I assume that Sinn regulates the movement before sending it to the customers.

ETA 2893-2 Movement (Credit Caliber Corner)

The bezel is made with the Tegiment technology and therefore especially scratch-resistant. This is a captive bezel with 60 clicks and it comes with a special design to prevent it from being lost.

All the figures and markers are engraved in the bezel. From 0 to 15, markers are in a black color and present every 30 seconds. From 5 to 60, the minute markers are red and the every 5 minutes figures remain black. At 12 o’clock the triangle is filled with super luminova and offers a fantastic visibility.

Engraved bezel with black & red markers www.dvkphotography.com

The bezel action is just perfect. Firm, precise and easy to use also with gloves. Of course, the alignment is just perfect as you can expect from Sinn.

The dial is painted black with white indexes and white hands also covered with Luminova and offers superb readability in dive or night conditions.

The red color is devoted to everything that is secondary to the function of the watch like the GMT hand and markers or the literature on the dial.
The form is always dictated by the function.

Please note the presence at 6 o’clock of the copper sulfate capsule that shows the level of saturation.

Sinn Ar-Technology capsule color

On top of the dial, the slightly domed 4.2mm thick and scratch resistant anti-reflective sapphire crystal with double Ar-coating offers an amazing readability on all occasions.

As I chose the steel bracelet, I’ll only speak about this option. Please note that the watch is also available with a large choice of leather and silicone straps.

The bracelet is a stainless steel two-link with a bead blasted look and a weight of 105 grams. I’m not a huge fan of bracelet but for this watch, it sounds like an evidence to me as it really matches the overall design of the watch.

Steel bracelet with a weight of 104grams www.dvkphotography.com

For those who know me, this does not prevent me from wearing the watch with other straps as I’m a straps freak 😉

However, my first choice is to wear the Sinn U2 with the original bracelet as it is really well made, comfortable and the clasp is one of the best on the market.


My conclusion about this Sinn U2 may not be 100% objective because of the story behind, me receiving the watch. But if you are looking for an uncompromising, solid watch that you will not be afraid to wear in all situations – this watch is for you. What could actually dampen buyers is this uncompromising look and also the size and weight of the watch that makes it an imposing object.

I hope you liked this review and please do not hesitate to send me your comments.


Technical Specifications:

Mechanical Movement

  • ETA 2893-2
  • 21 bearing jewels
  • 28,800 semi-oscillations per hour
  • Seconds stop function
  • Anti-magnetic as per DIN 8309


  • Case made of German Submarine Steel, bead-blasted
  • 4.2mm Sapphire crystal glass in front, anti-reflective on both sides
  • Pressure-resistant up to 200 bar, certified by DNV GL
  • According to the technical demands for the diving norm DIN 8306
  • Tested based on European diving equipment standards EN 250 / EN14143 and certified by DNV GL


  • Hours, minutes, seconds
  • Second time zone on a 24-hour basis
  • Date display
  • Diver’s bezel with minute ratcheting and luminous key mark

SINN Technologies

  • Bezel with TEGIMENT Technology
  • Ar-Dehumidifying Technology
  • Temperature Resistance Technology, therefore functionally reliable at temperatures from -45°C up to +80°C

Dimensions and Weight

  • Case diameter: 44 mm
  • Lug to lug: 52mm
  • Band lug width: 22 mm
  • Case thickness: 15.5 mm
  • Weight without strap: 114 grams
  • Bracelet weight: 105 grams with all the links

Dial and Hands

  • Matte black dial
  • Indices coated with luminescent colour
  • Hour, minute and second hand coated with luminescent colour