Precision is not a generic quality: it is the measurable result of design choices that accumulate on an infinitesimal scale. In mechanical movements, every tenth of a millimeter — sometimes every hundredth — changes the behavior of the system. This is what distinguishes a mechanical watch from any other object built by mankind: the number of interdependent technical constraints that must coexist in a tiny space.
The starting point in the industry is COSC certification. The Contrôle Officiel Suisse des Chronomètres, founded in 1973, accepts movements with a daily variation between -3 and +6 seconds. It is a serious standard, but over time it has become the baseline. Rolex introduced its Superlative Chronometer Certification, more restrictive: -2/+2 seconds per day, verified on the assembled watch. Omega went further with the Master Chronometer METAS — born in 2015 with the Globemaster — which certifies precision within 0/+5 seconds per day, magnetic resistance up to 15,000 gauss, and reliability in multiple positions. The Tudor MT5601-U follows the same protocol. These are certifications that measure complete systems, not just ebauches in the laboratory.
From the workbench I have learned that the precision of a movement depends on at least three variables that are difficult to control together: the constancy of the force transmitted by the spring, the stability of the balance wheel under external stresses, and the regulator's ability to ignore gravity. Each has its own technical solution. The remontoir d'égalité — used by F.P. Journe and Lederer in the Central Impulse Chronometer — regularizes the force to the escapement regardless of the barrel's charge state. The free-sprung balance, adjusted with screws rather than a fixed return spring, offers superior stability across temperature and position variations. The tourbillon, invented by Breguet in 1801, encloses the escapement and balance wheel in a rotating cage to neutralize the effect of gravity — especially effective in pocket watches worn vertically. The triaxial tourbillon, like the one in Desder's D001 designed by Luca Soprana, extends the principle to three simultaneous axes. Breguet with the Experimentale 1 pushed the frequency to 10 Hz: perturbations and impacts have less time to alter the oscillator between vibrations.
The balance wheel frequency is a direct factor: 28,800 beats per hour (4 Hz) is the modern standard in quality automatic movements. The higher the frequency, the finer the time subdivision, but also the greater the energy consumption and wear. The seconds stop mechanism — traditional in pilot watches — allows you to synchronize the movement to the exact second during regulation. A small thing, but practically useful. Horological metrology, that is, the science of measurement applied to movements, has been refined with technologies like Dual Metric Technology, which continuously reads frequency variations with high resolution. Tools like these change the quality of adjustment, not just its speed.