Our in-house testing certification
CHRONO10
Precision, Tested and Certified by Zero West
For those with a particular interest in the horological performance of their watch, we believe the details matter.
Every Zero West watch is fitted with a Swiss-made Sellita Top/Premium Grade automatic movement from the SW200 or SW500 family. We specify these higher-grade movements as standard, providing an excellent foundation for accurate, reliable mechanical timekeeping.
Why We Choose Sellita Top/Premium Grade Movements
Not all Swiss mechanical movements are created equal. Sellita manufactures its movements in several grades, from Standard through to Top/Premium, with differences in the materials, components and precision of their factory adjustment.
At Zero West, we exclusively specify Top/Premium Grade movements, which offer several important advantages:
• Superior balance wheel: Manufactured from Glucydur, a specialist alloy chosen for its dimensional stability and resistance to temperature-related changes, helping maintain consistent timekeeping.
• Precision hairspring: A higher-specification Nivarox alloy hairspring, engineered for consistent elasticity and improved temperature stability, helping the movement maintain a more consistent rate under changing conditions.
• Quality shock protection: Incabloc protection helps safeguard the delicate balance assembly against everyday knocks and impacts.
• More precise factory regulation: Top/Premium movements are adjusted in five positions to tighter accuracy tolerances, compared with the two positions used for Standard Grade movements.
The result is a movement built and regulated to a higher specification, providing a better foundation for accurate, consistent and reliable mechanical timekeeping.
We choose these movements as standard because we believe the quality of a watch should begin with the engineering inside it.
The Sellita Factory Standard
Sellita’s published Top/Premium Grade timing specification for the SW200 and SW500 movements is:
• Mean daily rate: 0 to +8 seconds per day (4 ± 4 seconds)
• Maximum positional variation: 15 seconds per day
• Factory adjustment: Five positions
• Operating frequency: 28,800 vibrations per hour (4 Hz)
These are the manufacturer’s production specifications, measured under defined test conditions, rather than guaranteed daily accuracy on the wrist.
Every Zero West Watch Is Individually Regulated
We don’t simply accept the factory settings.
During assembly in England, Russell, our watchmaker, individually checks and regulates each watch using professional Witschi electronic timing equipment.
Russell measures the watch in multiple positions to assess its rate, amplitude and positional variation. Where necessary, he makes further adjustments to optimise its timekeeping beyond the original factory setting.
This testing is conducted at the ambient temperature of our workshop and forms part of our standard assembly and quality-control process.
Every Zero West watch benefits from this individual attention, whether or not Chrono10 is specified.
CHRONO10 — Taking Precision Further
For customers who want a more comprehensive assessment of their watch’s timekeeping, we developed Chrono10, our own extended regulation, temperature testing and certification programme.
Inspired by the principles of the Swiss COSC chronometer testing system, Chrono10 has been developed in-house using our own dedicated testing equipment and procedures.
Unlike our standard workshop regulation, Chrono10 measures performance across six positions at three controlled temperatures:
• 8°C — Cold
• 23°C — Reference temperature
• 38°C — Hot
At each temperature, the watch is allowed sufficient time to reach thermal equilibrium, ensuring that the movement and surrounding assembly have stabilised before measurements are taken.
Russell then tests the watch in six positions at each temperature, providing 18 distinct temperature and positional test conditions.
This allows us to evaluate not only the average rate of the watch, but also the effects of gravity, orientation and temperature on its timekeeping.
Where necessary, Russell further regulates and retests the movement to optimise its performance across these conditions.
The Chrono10 Accuracy Standard
Our Chrono10 programme is designed to achieve a mean daily rate within the following limits:
−4 to +6 seconds per day
Our preferred regulation target is +2 seconds per day, providing a practical balance between fast and slow running within the specified tolerance.
The Chrono10 result is determined from the measured performance across our defined test conditions, rather than from a single timing measurement at room temperature.
Chrono10 is an independent Zero West testing and certification standard, not an official COSC certification.
Individually Certified in England
Every watch successfully completing the Chrono10 programme receives its own Zero West certification.
A physical Chrono10 test card accompanies the watch, documenting its individual measured performance and providing a permanent record of the testing undertaken.
The caseback is also marked CHRONO10 CERTIFIED, identifying the watch as having successfully completed our extended testing programme.
Chrono10 is an optional service. Our standard watches already benefit from Top/Premium Grade Swiss movements and individual in-house regulation.
For those who appreciate the finer details of mechanical timekeeping, Chrono10 offers something further: individually measured, documented and verified performance, using a testing process developed and carried out by Zero West.
CHRONO10 — Engineered, tested and certified in England.
