Standards
The certifications and tests behind a watch's accuracy, water resistance, magnetism and shock: ISO 6425, COSC and more.
The numbers and marks on a watch often rest on a standard. A chronometer certificate speaks to accuracy, ISO 6425 to dive capability, a gauss figure to magnetic resistance.
The terms in this section explain in plain language what each certification actually measures, so you can tell a real guarantee from a marketing line.
- Accuracy (Daily Deviation)
- Accuracy describes how far a watch drifts from true time, given in seconds per day. A quartz watch drifts a few seconds a month, while a good mechanical drifts a few seconds a day. It is a property of the movement type, not a fault.
- Antimagnetic
- Antimagnetic describes how well a watch resists magnetic fields. Magnetism can make a mechanical watch run fast or stop altogether, and the resistance is rated in gauss or to the ISO 764 standard. A soft-iron inner case or silicon parts add the protection.
- Chronometer (COSC)
- A chronometer is a watch whose movement has been tested and certified for accuracy by an independent body. In Switzerland that body is COSC, and the movement must keep to about minus four to plus six seconds a day. It is an accuracy grade, not the same thing as a chronograph.
- Japan Movement
- Japan movement is a label meaning a watch's movement was made in Japan, by makers such as Seiko, Citizen, or Orient. Japanese calibers are known for being reliable, accurate, and affordable. Japan made usually refers to the whole watch, while Japan movement points only to the engine inside it.
- Shock Resistance
- Shock resistance is a watch's ability to survive drops and knocks without losing accuracy or breaking, often measured against the ISO 1413 standard. Shock springs cushion the balance so it absorbs the hit. The Casio G-Shock is built entirely around this idea, floating its movement inside the case.