Known for its military-inspired instrument watches, Sinn revisits one of its signature models with the 903 St II Navigation Chronograph. Updated in terms of the movement and case, the new 903 makes its debut with three dial variants, including a limited edition featuring an attractive light blue dial.

Initial thoughts

The 903 St is curious for bearing a striking similarity to the Breitling Navitimer – a result of Breitling having sold the rights to produce the Navitimer when it went bust during the Quartz Crisis. While the earliest versions of the 903 were essentially rebadged Navitimers – Sinn having bought the components from Breitling – the new 903 is a Sinn creation and also better than previous generations.

The 903 St II in classic black

Compared to earlier generations of the model, the 903 St II is streamlined and improved. Upgrades include removing the fiddly second crown at ten (so the slide rule is now directly operated via the bezel), the addition of luminous blocks for indices, and an applied logo. 

The appeal of the new 903, however, does have one caveat: the date between four and five remains, but only on the regular production version. It’s absent on the limited edition, but that arguably should have been done for all variants. 

The standard 903 St costs US$3,730 with a leather strap, and an additional US$240 for a bracelet. The 500-piece limited edition model is priced at US$4,170. The affordable price makes it a more attractive proposition than many other aviation chronographs, particularly those powered by the same La Joux-Perret calibre. But the 903 is not quite the signature Sinn pilot’s chronograph, which would be the more affordable 103.

The earlier generation 903 St with the second crown at ten

Updated and refined in design

During the Quartz Crisis of the 1970s, Breitling eventually went under, leading to its liquidation. The rights to produce the Navitimer, as well as Navitimer components like cases and dials, were sold to Sinn. Other companies, including Ollech & Wajs also bought bits and pieces of Breitling (Ollech & Wajs then sold Navitimers under the “Aviation” brand). Most of the inventory went to Sicura, which was owned by Ernest Schneider, who later bought the Breitling name as well.

The new 903 retains the familiar Navitimer features, including the three-register dial and bi-directional slide rule bezel, a tool for pilots to calculate flight times and distance. Three dial colours are available: black, dark blue, both with a sun-ray finish; and a limited edition in light blue. Notably, the date disc is tone-on-tone while the limited edition omits the date entirely..

All versions of the new 903 share silvered registers that contrast with the dial, along with applied markers and inserts on the hands made of luminous ceramic composite. Additionally, the Sinn logo at 12 is applied instead of printed.

The light blue 903 St HB

Aside from cosmetic changes to the dial, the steel case has also been redesigned. Originally used to rotate the bezel, the second crown at ten is now gone. Additionally, the new case has a water resistance rating of 200 m, up from 100 m before.

Sinn managed to all do that without changing the case dimensions, which remain the same at a manageable 41 mm in diameter and 14.5 mm high, essentially identical to the Navitimer of the 1960s.

The dark blue St B E II

Through the display case back the La Joux-Perret L110 is visible. Derived from the Valjoux 7750, the L110 has a substantial 60-hour power reserve and operates at 4 Hz. The original architecture was modified to replace the cam with a column wheel, but the oscillating pinion was retained.

The limited edition model is powered by the LJP 112 that lacks the date but otherwise identical.

Key facts and price

Sinn 103 St II Navigation Chronograph
Ref. 903.090 (St II, black)
Ref. 903.091 (St B E II, dark blue)
Ref. 903.095 (St HB, light blue)

Diameter: 41 mm
Height: 14.5 mm
Material: Stainless steel
Crystal: Sapphire
Water resistance: 200 m

Movement: La Joux-Perret L110 or L112 (only for the limited edition)
Functions: Hours, minutes, small seconds, date, chronograph with central seconds (no date function for the limited edition)
Winding: Automatic
Frequency: 28,800 beats per hour (4 Hz)
Power reserve: 60 hours

Strap: Matching bracelet or leather strap

Limited edition: Regular production except for the St HB which is limited to 500 pieces
Availability: At Sinn retailers
Price:
St II & St B E II : US$3,730 (strap); US$3,970 (bracelet)
St HB: US$4,170

For more information, visit Sinn.de.