The Precision of a Rolex Superlative Chronometer is of your order of −2/+2 seconds a day – the speed deviation tolerated because of the brand name for your concluded watch is considerably scaled-down than that recognized by COSC for Formal certification with the movement by itself. The Superlative Chronometer status https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/