A former Rolex insider who gave me a lot of the info on the OQ perpetual calendar movements has told me that there was one substantive change to the 5035 and 5055 movements that took place approximately 18 months after they were introduced for sale to the public. The quartz crystal was changed to one cut in the shape of a tuning fork. He didn't elaborate on the previous shape. He just said the earlier movements were known internally at Rolex as Mark I movements and the later ones were known as Mark II. Only Mark II 5035 movements were submitted to the COSC for chronometer certification, which would explain why the early Datejust OQs didn't have the "Superlative Chronometer Officially Certified" wording on the dials.