Anti-reflective coating

The anti-reflective coating is an optical coating applied to the inside surface of the crystal to reduce reflection. The coating consists of alternating layers of contrasting refractive index that improves readability by eliminating stray light and reflection.

Calibre 13 Phi and 13 Upsylon

Our calibre 13 Phi (uni-compax flyback) and 13 Upsylon (uni-compax) are custom made with modified Valjoux 7750™ movements from ETA.

Designed by Edmond Capt in the early 1970's, the Valjoux 7750™ was the first mechanical movement developed thanks to CAD. Sized at 13" French lines by 7.9 mm in thickness, this calibre capitalized on Valjoux SA (Société Anonyme = Public Limited Company) expertise with integrated complications to offer as a cost-efficient self-winding cam chronograph. It was introducing a new breed of higher speed regulating parts called Clinergic (28,800 alternances per hour or 4 Hz). Production began in 1974, and some 100,000 movements found buyers1 even though production was halted between 1975 and 1985 while the Swiss industry was being restuctured2, but resumed under ETA SA.

Siduna calibre 13

Compur arrangement

The "compur" arrangement was coined by brands such as Universal and Zenith as early as 19363 to describe their chronographs. It initially referred to the amount of complications of the movement but it evolved to describe the arrangements of subsidiary dials.

Since most chronographs feature one subsidiary dial that shows the running seconds, a Uni-Compax dial features one additional subsidiary dial, a Compax features two additional subsidiary dials in a symmetrical V-shaped arrangement with the running seconds, and a Tri-Compax features three additional subsidiary dials.


Fly-back feature

The Flyback feature was developed to allow professionals to allow pilots to stop, reset and start the chronograph with a single command.

Full grain leather

Our straps are manufactured in Germany with full grain leather and undergo more than 70 different manual steps. Full grain leather is a fine and luxurious material, which top layer has been preserved to show the natural grain. It is the area of the hide with the highest density of fibres, to which it owes its resistance, softness and smooth touch. Leather is a natural material with a texture and flaws that take a nice patina with time.

In order to keep your top grain strap a long time, we recommend to remove the watch for sleeping and to avoid getting it wet or subjecting it to heat or sunlight. As a natural material, leather is sensitive to wear and fatigue.

full grain leather - black
full grain leather - havana
full grain leather - rouille

ISO 764 Magnetic resistant

ISO 764 specifies the minimum requirements and test methods for magnetic resistant watches. It is based on the simulation of an accidental exposure of a watch to a direct current magnetic field of 4 800 A/m.

ISO 1413 Shock-resistant

ISO 1413 specifies the minimum requirements for shock-resistant wrist watches and describes the corresponding test method. It is based on the simulation of the shock received by a wrist watch while falling from a height of 1 m onto a horizontal wooden floor

ISO 22810 Water-resistant

ISO 22810 establishes the requirements and specifies the test methods used to verify the water resistance of watches. Moreover, it indicates the marking which the manufacturer is authorized to apply to them.


Our nubuck leather is a top grain leather where the upper layer has been sanded off to give a matte surface with a rich and evolving velvet touch.

nubuck - asphalt
nubuck - wenge
nubuck - mocca


Physical Vapour Deposition is a vacuum surface-coating process that deposits a layer of high density material with only a few microns of thickness. Once applied, the coating is extremely hard to remove, and it will not wear off on its own.

Sapphire crystal

Synthetic sapphire is created by applying incredibly high heat and pressure to aluminum oxide powder. The resulting material is nearly twice as hard as standard glass and nearly as hard as diamond.

Screw-down crown

The earliest idea behind a screw-down crown, to use a treat to apply pressure to a sealant, was patented by Ezra C. Fitch in 18814 and later improved by Girard-Perregaux and Rolex in 1925 to lead to the modern screw-down crown.

1881 US patent US237377 by Ezra C. Fitch

Stainless steel

The current stainless steel alloy favored by the watch industry is SAE 316L, with the "L" indicating an extra-low carbon content. It is very similar to the Staybrite SAE 304 that Siduna started using in the mid 1920's, but its slightly higher content in carbon, nickel and chromium makes it even more resistant to corrosion. [Illustration: Schaeffer diagram, credit The Welding Institute. Reproduced under fair dealing (s32)].



Super-LumiNova® is the trademark of a non-toxic and non-radioactive strontium aluminate photo-luminescent pigment manufactured by RC Tritec AG of Switzerland, a joint venture with Nemoto & Co., Ltd. of Japan. When mixed with a binder and applied on the dial and hands, it allows the resulting shapes to glow in the dark after exposure to ultraviolet light.

The M3440 Professional Chronograph uses Super-LumiNova® Blue Line (485 nm) C3 Grade A, which offers optimal photo-luminescence in extreme environments.

Super-LumiNova Blue Ligh C3 Grade A

Jewels synthetic ruby by PIerhor, reproduced under fair dealing (s32)Synthetic bearing rubies

Perforated natural rubies were originally used after 1700 for bearing the pinions of a watch. Around 1902, Verneuil managed to synthetise red aluminium oxyde with all the properties of natural ruby [Illustration: synthetic ruby by Pierhor SA, Switzerland, reproduced under fair dealing (s32)].


1. Valjoux 7750 at Watch-Wiki.net
2. History of the ETA 7750 and TAG Heuer by Calibre11
3. Chronographs of Universal Geneve Compax series - Part 1 by Noodia
4. The evolution of the waterproof watch by David Boettcher