Rolex Precision Square 18k yellow ref. 3404-3

Unlike Datejust or Sea-Dweller, Precision is technically not a model name. It is simply a description of the specifications of the caliber inside.

You may be familiar with COSC-certification. Contrôle Officiel Suisse des Chronomètres, is an independent non-profit institute that performs accuracy testing of Swiss made watch movements. Every individual movement, identified by its serial number, is tested and certified as a chronometer if it meets a set of standards. The most familiar is an average maximum daily deviation of +6/-4 seconds for mechanical movements. Today, about 3% of Swiss watches is chronometer rated. Rolex is, by numbers, the largest player in COSC-certified watches.

Most Rolex movements are chronometers. Many even underwent additional testing by Rolex themselves, to be labeled Superlative Chronometer. There are, however, Rolex movements that have not been externally certified for accuracy.

Famous are the Ref. 5513 Submariners. They did not feature individual movement numbers, indicating they were not chronometer certified. The Ref. 5512 was the chronometer variant, simultaneously available.

Another example are the Precision-labeled watches from Rolex. These were manually wound calibers, tested by Rolex themselves. A common variant is the Oyster Precision, which is a manually wound, time-only watch in the familiar Oyster case. Do not be fooled though, the Rolex quality is all there!

Several non-chronometer models are available under the Precision label. Besides the time-only Oyster Precision, a manual-wound non-chronometer Oysterdate Precision in 34mm case can also be found. This model is, in appearance, very similar to the more common Oyster Perpetual Date, but with a manual, non-chronometer caliber.

Today, all Rolex movements are automatic (perpetual) and COSC-rated. So to own a Precision caliber by the famed house is to own a piece of watchmaking history.