The Precision of the Rolex Superlative Chronometer is from the order of −2/+2 seconds each day – the speed deviation tolerated via the model to get a completed check out is noticeably smaller than that acknowledged by COSC for Formal certification with the movement on your own. The Superlative Chronometer https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/