Regulation Marking — What This Mark Means

Regulation markings indicate the adjustment directions for the regulator, the mechanism that controls a mechanical watch's timekeeping rate. Typically shown as "+" and "-" or "F" and "S" (Fast and Slow), they guide adjustments to the effective length of the balance spring: shortening it makes the watch run faster, lengthening it slower.

The adjustments involved are tiny. A barely perceptible movement of the regulator arm can change the rate by several seconds per day, which is why most modern ETA and Sellita movements use the Etachron system, designed to make fine regulation more controlled. These markings are relevant only to mechanical movements.

The markings sit on the movement near the balance wheel assembly, usually engraved or printed on the balance cock next to the regulator lever, the small adjustable arm above the balance. They are visible through an exhibition case back or when the case back is removed.

Some quartz movements, particularly older ones, have a small trimmer capacitor for rate adjustment instead, though this is uncommon on modern quartz.

Common markings include "+/-" symbols, "F/S" (Fast/Slow), and "A/R" (Avance/Retard, the French equivalent, common on Swiss and French movements). Vintage movements sometimes spell the words out or add graduated scales, and higher-grade movements may use a swan-neck fine adjuster with a screw.

High-end calibers often have no regulator markings at all: free-sprung balances such as Rolex's Microstella system or Patek Philippe's Gyromax adjust the rate with weights on the balance wheel itself, a more stable arrangement.

The markings do not mean the owner should adjust the watch. Regulation requires a timegrapher and experience, and amateur adjustments can easily make accuracy worse or damage the hairspring. "ADJUSTED" engraved on a movement means it was factory-adjusted to standards in multiple positions, not recently regulated.

Conversely, "UNADJUSTED" on vintage movements imported to the United States was often a tariff-related classification and does not mean the movement is poorly made.

If your watch runs outside acceptable limits, take it to a qualified watchmaker for regulation rather than attempting it yourself. As reference points, COSC chronometer certification requires -4 to +6 seconds per day, while entry-level automatics are often specified in the range of -20 to +40 seconds per day.

Regulation is normally checked as part of a routine service every three to five years.