06/04/2020
 7 minutes

Sinn 203 St: A Diving Chronograph With Pilot’s Watch Potential

By Sebastian Swart
CAM-1238-Sinn_2-1

Sinn 203 St: A Diving Chronograph With Pilot’s Watch Potential

German watchmaker Sinn first introduced their 203 St diving chronograph in 1995. The original model was water resistant to 300 m (30 bar, 984 ft) and equipped with a diving bezel. It was the underwater counterpart to the beloved Sinn 103 pilot’s watch, which made its debut in the 1960s. While the diver was visually appealing, solidly built, and reliable, it never quite won people’s hearts over like the 103 and was subsequently discontinued.

About the Sinn 203 St

Former pilot and flight instructor Helmut Sinn founded his company, Helmut Sinn Spezialuhren, in Frankfurt, Germany in 1961. Sinn has been crafting high-quality tool watches for motorsport, diving, and aviation ever since.

Sinn 203 St
Sinn 203 St

Sinn garnered plenty of attention for their 101, 102, and 103 pilot’s chronographs. These three lines are renowned among collectors to this day. Though some watches in the 103 line can double as divers, they are first and foremost pilot’s watches. One of the main aesthetic differences between the 103 St and the 203 St are the latter’s obelisk-shaped hands. Moreover, the 103 St features a black aluminum bezel inlay, while the 203 has a luminous zero marking. In terms of water resistance, the 203 St and its stainless steel case back boast a depth rating of 300 m (30 bar, 984 ft). The same model with a sapphire crystal case back, as well as the 103 St, can “only” withstand depths of 200 m (20 bar, 656 ft). A few months ago, I acquired a 1999 203 St with a sapphire crystal case back for my own personal collection, which has in large part inspired this article.

I first saw the chronograph online in February 2020. The asking price wasn’t exactly a bargain – especially considering the watch didn’t come on its original stainless steel bracelet – but it was still reasonable. I found out from the seller that the 203 St in question had only ever had one owner, was rarely worn and in like-new condition, and came with the original receipts and service documents. I had no choice but to click the “buy now” button.

Technical Details of the Sinn 203 St

The Case

The polished stainless steel case is a so-called “compressor-style” case. In typical Sinn fashion, the construction is impeccable and the finishing flawless. Sinn has had their cases manufactured by the  Sächsische Uhrentechnologie GmbH Glashütte (Saxon Watch Technology Glashütte, SUG) since 1999, but I haven’t been able to find out if they were the makers of my watch case or not. Sinn typically delivers the 203 St with a screw-down stainless steel case back; however, the original owner of my watch opted for a sapphire case back, which reduces the water resistance from 300 m to 200 m (20 bar, 656 ft).

Sinn 203 St
Sinn 203 St

Of course, this hardly makes any difference in your average everyday life, myself included. In any case, the display case back offers a clear view of the Valjoux 7750 caliber at work. The pushers and crown are screw-down, which prevents accidental adjustments and adds additional protection against moisture. The case meets the DIN 8310 standards for water-resistant watches.

Size, Weight, and Wrist Comfort

The Sinn 203 St is 41 mm wide, and the bezel measures almost exactly 40 mm across. Overall, these proportions make the watch a suitable choice for all wrist sizes and shapes. The watch measures 47 mm from lug to lug. However, since my model is 16 mm thick and has a domed sapphire crystal case back, the lugs sit some distance away from the wrist. This can’t be avoided given the shape of the watch, but it is certainly a matter of taste worth considering. Without the bracelet, the watch weighs 90 g (approx. 3.2 oz), which gives it a nice presence on the wrist. For comparison, an Omega Speedmaster with arcyrlic glass weighs just 65 g (approx 2.3 oz).

Due to the relatively small area of contact with the wrist, I don’t think the 203 St is wears well on a NATO strap. Likewise, its weight and thicknes make it too heavy for a loose-fitting metal bracelet. The best solution, in my opinion, is to wear the 203 St on a snug leather strap. Purists may argue that diving watches don’t belong on leather straps, but I’m definitely open to the idea. If you want to take the watch for a dive or swim, it’s easy to switch to a rubber strap. The lugs sit 20 mm apart, which allows for a wide selection of band options. Plus, it’s fun to change straps every now and again.

Sinn 203 St with a leather strap
Sinn 203 St with a leather strap

The Valjoux 7750 Movement

The 203 St is powered by the Valjoux 7750, an automatic chronograph caliber made by Swiss movement manufacturer ETA. This movement has been in production since 1973. It’s considered a durable and reliable movement that is relatively easy to service. ETA manufactures the caliber in three different quality grades: elaborated, top, and chronometer. According to my research, Sinn uses a top-grade 7750 in the 203 St. This means the movement is regulated in five different positions and deviates no more than +/- 4 seconds per day. My watch doesn’t quite live up to those standards, but then again, it hasn’t been serviced since 2004.

 The 7750 features with 25 rubies and ticks at 28,800 A/h. Sinn opted not to decorate any of the individual movement components, likely because the watch is typically delivered with a solid case back.

Sinn 203st

Functions of the Sinn 203 St

A watch’s functionality primarily depends on the movement. The Valjoux 7750 features three complications: a chronograph, date display, and day display. The small seconds and chronograph subdials are located at 6, 9, and 12 o’clock, while the day-date display is at the 3 o’clock position. The hour, minute, and stop seconds hands all sit centrally. The dial looks like a typical pilot’s watch and is styled after old onboard navigation clocks.

The matte black dial is outfitted with Arabic numerals and square indices filled with luminous material. My watch has tritium on its dial, but Sinn has since made the switch to SuperLuminova. Unfortunately, the tritium has lost most of its glow after all these years. Watches with tritium dials feature “T” symbols to the left and right of “Swiss Made.” At the time, Sinn watches were all made in Switzerland, earning them that designation.

Sinn 203st

How functional is the Sinn 203 St?

Sinn has always placed a lot of emphasis on creating functional tool watches. They value perfect readability, ease of use, and durability. I’m not a diver, so I can’t say much about how this 21-year-old watch fares underwater, but it did pass its water resistance test. I have no complaints about the pushers, crown, bezel, or any of the chronograph functionality. Everything switches and clicks cleanly and reflects high production quality. My only complaint rests with the pusher screws. They are remarkably small, even for medium-sized fingers. Plus, they are really difficult to release after being locked in place.

Sinn 203 Variations

A particularly interesting version of the Sinn 203 St is the “Bell & Ross by Sinn.” This watch also dates back to the mid-1990s and features identical construction and functionality. The only differences are that the Sinn logo is replaced by the text “Bell & Ross by Sinn” and the watch features a different set of hands. This collaboration came about because one of Bell & Ross’ co-founders worked at Sinn at the time. Back then, Helmut Sinn was still directing his company and agreed to produce a limited number of watches under the Bell & Ross name.

Sinn 203 Arktis I
Sinn 203 Arktis I

In 1999, Sinn introduced the 203 Arktis. Unlike the standard 203 St, this watch has a UV-resistant blue galvanized dial. It also features Sinn’s own Ar-Dehumidifying Technology, which further prevents moisture from building up inside the case. The watch is functionally reliable in temperatures ranging from -45°C to 80°C (-49°F to 176°F). The original 203 Arktis was succeeded by the 206 Arktis II in 2019. This watch is visually and technically very similar to the original Arktis model, but it is 2 mm larger at 43 mm diameter.

In addition to the standard stainless steel 203 St, Sinn also makes a 203 Ti version out of titanium. This watch also features Sinn’s Ar-Dehumidifying Technology. A special edition “203 Anniversary” titanium chronograph was released in 2006 to mark the company’s 45th anniversary. This model comes with a so-called “reverse panda dial” with white subdials.

Availability and Price

The 203 line is no longer in production, making it difficult to find unworn models; however, there are plenty of pre-owned examples on the market. Expect to pay between $1,550 and $2,200 for a standard used 203 St. The 203 Arktis sells for slightly more with most prices north of $2,200. You’ll occasionally find the 203 Anniversary model on Chrono24 for around $3,300. The 203 “Bell & Ross by Sinn” sells for roughly the same amount as the standard edition.

Summary

The Sinn 203 St is a solid chronograph with has very few weaknesses. In terms of reliability and durability, this watch holds its own against much more expensive timepieces from more famous brands. The robust Valjoux 7750 movement won’t win any prizes for exclusivity, but it does the job with a high level of precision and longevity. You’ll have to ask divers out there whether this timepiece ticks all the boxes in terms of readability and functionality underwater. However, given the relatively small crown, screw-down pushers, and comparatively busy dial, I could imagine that other diving watches outperform the 203 St in that department. That said, the Sinn 203 St is a versatile watch that is beautiful to behold. While various band options are available, I prefer to wear mine with a leather strap given the thickness of my watch’s case and domed sapphire case back.

Read more

Sinn at Baselworld: Two Special Editions of the Sinn Financial District Watch

Sinn Watches: 3 (Vintage) Models for Collectors


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About the Author

Sebastian Swart

I've been using Chrono24 for years to buy and sell watches, as well as for research purposes. I've had an infatuation with watches for as long as I can remember. As a …

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