Sinn U50

The Sinn U50 is a tool watch in a class of its own. In a time when every timepiece with a bezel is being labeled a “tool”, Sinn divers are the epitome of tough, well-engineered machines.

For most tool watches, 316L stainless steel is enough. For some, 904L steel is required. The U50 goes against the tide with its seawater-resistant German Submarine Steel.

“The case and crown are thus made of high-strength seawater-resistant German Submarine Steel. This type of steel stands out not only for its extremely high strength and exceptional non-magnetic properties but also for its especially high resistance to seawater.” -Sinn

All of this is formed into an architecture that measures 41mm in diameter with a thickness of 11.2mm. The tug-to-lug spans 45.5mm across the wrist.

The blasted “sub steel” case is topped off with a 60 click uni-directional rotating bezel is made from Tegimented steel, making it harder and more scratch resistant. The rotation feeling is firm and snaps into place without any back play.

The crystal is a flat sapphire with anti-reflective coating on the top and bottom. Just look at the image above and you can see how crisp it is, even when held at an angle.

If you are familiar with Sinn, then you may have seen that their cases are signed with SUG between the lugs. This mark stands for Sächsische Uhrentechnologie GmbH, a Glashutte based watch case machine shop, and partner of Sinn.

The SUG logo on the U50 is slightly different than on other models. On the U50, it simply says SUG, but on other Sinn watches the logo has Germany written beneath it. This difference is presumably due to the thinness of the case and lack of real estate for such adornments.

If you know you want a Sinn diver but can’t decide between the U50 or U1, just know that the U50 is the comfort-seeker’s tool watch. With a height below that of a Rolex Submariner, the U50 is more manageable on the wrist than the U1. If big, bold and chunky are what you look for, go for the U1.

Sinn will sell you a U50 on a wide variety of straps, but most common are the steel bracelet or silicone strap. Most collectors go one way or the other, although it doesn’t hurt to have options. When it comes to silicone, there are 3 types of connectors available: regular tang buckle, small folding clasp, and a larger folding clasp.

The clasp on this watch is the smaller style, which is much more comfortable on the underside of the wrist. It features two holes on each side, allowing for micro-adjustments due to seasonal temp changes or weight loss or gains without having to size the strap.

There is some wear on this clasp, something you will likely come across and something to keep in mind. The U50 has a bead blasted finish which look amazing, but as tough as it is, marks do show up. For the pic below, you can’t really tell there is a scratch at a glance, but held at the right angle in the light, you can see it. The photo intentionally exaggerates the wear to demonstrate this. Other watches with a satin or polished finished may be easier for you to do a DIY clean-up of inevitable scratches or blemishes, but bead blasted watches require being hit by the blaster to blend in any marks. It’s something that can be handled when sending a watch in to the manufacturer for routine service.

The double push-button action is secure and smooth to click in and release. The silicone straps are cut-to-size style, which is why the micro-adjustment holes are nice to have in case you need to adjust it without wanting to cut another section off. The clasp is signed “Edelstahl” aka stainless steel in German.

Something else you should know about the silicone… it is an absolute lint magnet. You could probably use it as a lint brush in a pinch.

Behind the minimalist caseback is a Sellita caliber SW300-1. This 3.6mm thick machine is based on the ETA 2892-A2, with 25 jewels and a beat rate of 28,800 vph. The caseback has notches for easy access, and protecting the seal is a green Viton gasket that Sinn is known for using.

There is a Sinn logo signed on the rotor of the movement. Below is an image from my other site:

On the dial side, the U50 uses a black background datewheel with white numbers. This would be a custom datewheel to accommodate both the colorway and the 4:00 crown position. As it has become obligatory in a watch review to mention hacking and hand-winding: yes, this movement is hackable and hand-windable. By the way, the screw-down crown system also features an inner green Viton seal (seen here).

Drilled lugs are another nice tool watch feature you can see in the image below. This allows for easier strap changing. Other luxury “tool watches” have gone from pierced (or drilled) lugs to smooth lugs as they transitioned from being tools to jewelry, but Sinn keeps it real – they also include a strap changing tool that fits perfectly in the hole.

The 4:00 crown is signed with an S, although it would have been better if they used the signature S from the Sinn logo.

Text on the dial reads U50 / Automatik / 500 m/50 bar / Made in Germany. In Germany, automatic is spelled with a K. The Made in Germany is printed in black and is sometimes not easy to see, but it’s there.

With the lights off, the lumeshot offers something different than the typical circles and rectangles used in most dive watch designs. Sinn does not specify if the lume material is Super-LumiNova, they only describe it as luminescent colour. Also notice that you get a larger sized lume pip than is found on other pieces.

Additional Resources:

Detailed Specs:

Reference: 1050
Movement: Automatic, Swiss made
Caliber: Sellita SW300-1
Case: Bead blasted submarine steel
Diameter: 41mm
Thickness: 11.2mm
Lug-to-Lug: 45.5mm
Dial: Black with white markers and red accents
Date at 3:00
Bezel: Uni-directional rotating with lume pip
Scratch-resistant sapphire crystal with AR on both sides
Sinn black silicone strap
Sinn double push-button small folding clasp
Lug-Width: 20mm
Crown: Screw-down
Water Resistant up to 500m

Includes: Sinn box and papers (outer black cardboard box, inner box, watch holder, U50 user manual, card folder, card signed and dated January 2023), strap tool.

Condition: Near mint overall, with exception to a desk diving blemish on the clasp – it could be blasted out. The silicone strap has been sized to fit about a 7.5″ wrist.