The Precision of a Rolex Superlative Chronometer is with the purchase of −2/+2 seconds a day – the speed deviation tolerated through the model for any completed watch is appreciably more compact than that accepted by COSC for Formal certification of the movement alone. The Superlative Chronometer status is symbolized https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/