ROLEX Crown Diameter: Approximately 6mm, Total: Approximately 6.5mm + attachments Stainless steel, Underbar engraving Twinlock type This is from a Datejust. I believe the part number is B24-600-0, but I'm not certain as I don't know much about it. If that's the case, the following models share the same part number: 1002 1016 1019 1500 1600 1601 1603 5500 I only looked this up and listed it, so I won't be able to answer detailed questions. I'm listing this in the hopes that someone can make use of it. Thank you.