The Precision of the Rolex Superlative Chronometer is in the order of −2/+2 seconds each day – the speed deviation tolerated because of the model to get a completed check out is noticeably scaled-down than that accepted by COSC for Formal certification from the movement by itself. The Superlative Chronometer https://www.watchesworld.com/understanding-the-complex-world-of-chronometers/