The Precision of a Rolex Superlative Chronometer is with the order of −2/+two seconds per day – the speed deviation tolerated with the manufacturer for a completed look at is noticeably scaled-down than that approved by COSC for official certification on the movement on your own. The Superlative Chronometer status https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/