Remember to Observe that commencing in 2005, Rolex commenced engraving the serial amount about the internal bezel (also known as the rehaut) underneath the crystal in the 6 o’clock posture. When the crystals within the 160xx era of Datejust watches are still produced from acrylic, the sloped "pie pan" model https://www.watchesworld.com/a-history-of-watch-reference-numbers/