Be sure to Observe that commencing in 2005, Rolex commenced engraving the serial amount within the internal bezel (also called the rehaut) beneath the crystal in the 6 o’clock place. Whilst the crystals on the 160xx era of Datejust watches remain comprised of acrylic, the sloped "pie pan" style dial https://www.watchesworld.com/a-history-of-watch-reference-numbers/