This is a GORGEOUS Rolex men's 40mm Oyster Perpetual Yachtmaster automatic watch, reference number 16623. It has a "Z" serial number. That dates its manufacture date to 2006.
It comes all-original with 18k yellow gold bezel and factory Rolex Black Tahitian Mother-of-Pearl dial as shown.
It did not comes with Rolex box or papers, but is 100% guaranteed authentic and accurate as described. The owner says he has the papers somewhere. If found, they will be sent free even after the sale. But for now it is offered without.
It is as follows:
CASE: 40mm (not including the crown) stainless steel case, with Rolex signed crown and 18k yellow gold Yachtmaster bezel. It has a Rolex scratch-resistant crystal in great condition, and solid case-back.
BRACELET/STRAP: Original Rolex signed stainless steel & 18k yellow gold "Oyster" bracelet shown with Rolex fold-over clasp. It looks amazing as shown, and is full-sized with 13 links.   
DIAL: Rolex factory Tahitian Mother-of-Pearl dial with: luminous markers; 18k gold hour, minute and sweep second hands; with date at h3.
MOVEMENT: Rolex automatic movement, Calibre 3135. It features: hours; minutes; seconds; and date. This is a "quick-set", which means the date can be set independently without having the hour hand pass midnight. It is keeping good time as noted above.
It is 100% guaranteed authentic and accurate as described and is offered with no reserve.