Sinn 903

• A navigation chronograph with a slide rule bezel
• An affordable alternative to the Breitling Navitimer
• Resistant to low pressure, shocks, magnetism, and water up to 100 m (328 ft)
• Highly precise Swiss automatic movements refined by Sinn
• A large selection of leather, steel, and silicone bands

The 903 navigation chronograph has been part of the Sinn Spezialuhren catalog since 1979. Its special features include the ability to measure periods of time and make mathematical calculations and conversions via its slide rule bezel.

The scales for the slide rule around the edge of the dial define the look of this chronograph. The outer portion can rotate in both directions to set the values for whatever calculation you're making. On older models, this took place via the bezel, while current models use an additional crown at 10 o'clock. Other details include a date at 4:30 and three subdials: a 30-minute counter at 3, a 12-hour counter at 6, and a small seconds at 9 o'clock.

Despite its many small numerals and markers, the dial still looks tidy. This is aided by the absence of all the hour numerals except the 12. The other hours are represented by luminous baton indices. Since the hands are coated in the same luminous material, you'll always be able to tell the time, even in the dark.

The retro charm of this elegantly sporty 903 is completed by a steel, leather, or silicone band.

The current Sinn catalog contains three versions of the 903. Bar their dial colors, these 41-mm stainless steel watches are identical. The 903 St stands out the most with its white silver-plated subdials, slide rule bezel, and white indices and hands. All of that contrasts beautifully with the satin galvanized black dial.

Then there's the 903 St Silber. Its entire dial is silver-plated and features black hands and indices. Combined with a leather strap, this model makes a stunning dress watch. The third and final model, the 903 St B R, has a certain retro charm. Its subdials and outer ring are both silver-plated, while the central dial is a luscious dark blue. The hands and indices come in the same ivory hue as aged luminous material.

From a technical perspective, all three models are identical: The automatic Sellita caliber SW 500 ticks inside each watch at a rate of 28,800 alternations per hour. It also provides these watches with their stop seconds mechanism and quick-set date. What's more, each timepiece is water resistant to 100 m (10 bar, 328 ft), shock resistant according to ISO 1413, and anti-magnetic in accordance with the German DIN 8309 standard.

You can purchase a current Sinn 903 in mint condition for between 3,000 and 3,200 USD. That price range falls to 2,100 to 2,500 USD for pre-owned pieces.

The Sinn 903 has appeared in many variations since its initial release. Some are highly coveted among collectors, such as the 903 H4 Moonphase. This watch is special in many ways: In addition to having subdials for the small seconds, elapsed minutes, and elapsed hours, it also features a fourth subdial at 12 o'clock. This additional subdial serves as both a moon phase indicator and pointer date . The manual Lemania caliber 1883 makes these extra complications possible. You can view this movement at work through the sapphire glass case back. Another deviation from the standard model is the position of the crown that controls the slide rule bezel: On this timepiece, it's at 8 instead of 10 o'clock. A well-maintained example of this collector's item sells for around 3,600 USD.

Another interesting model is the 903 H2. Its dial has only two subdials: a 30-minute counter at 3 and a small seconds at 9 o'clock. It's also powered by a Lemania movement, namely the manual caliber 1872. Fewer than 100 copies of this watch were ever produced, meaning it's extremely rare today. Plan to spend about 4,100 USD on this timepiece.

The 903 GL 24 is also a popular collector's item. Instead of the usual 12-hour display, it shows the time using a 24-hour display. This means the hour hand needs one full day to complete one rotation. It gets its power from the manual Lemania caliber 1877. While this model lacks a date display, it does still have the slide rule function, which is operated via the bezel. Depending on its condition, expect to pay anywhere from 3,400 to 4,000 USD on this watch.

Collectors also enjoy standard models from previous decades. Watches from the early 1980s with the manual Valjoux caliber 7740 cost around 3,300 USD in good condition. You can save some money by purchasing a timepiece from after the turn of the millennium powered by the automatic Valjoux 7750. These watches sell for about 2,900 USD.

The Sinn 903 is often incorrectly considered a copy of the Breitling Navitimer. If you look at them next to one another, the similarities are truly astonishing. However, there's a simple explanation for this:

At the height of the quartz crisis, Breitling was in financial distress. They had to close the majority of their production sites and all but stopped making watches. Businessman Ernst Schneider ended up buying the rights to the Breitling name and brand, but had no desire to take on their facilities, components, or movements. Helmut Sinn recognized the opportunity and purchased a large portion of the remaining components and movements, thus guaranteeing himself the right to continue building the watch under his own name.

In reality, the Sinn 903 is the twin sister of the Navitimer. It is an affordable alternative to the original and has developed into its own model with its own special features since its debut in 1979.