Tudor Black Bay GMT Mens Watch Tudor Black Bay GMT stainless steel automatic mens watch. Black dial, date, case diameter: 41mm, wrist size: 20.5cm, Swiss made. Ref# 79830RB. With Tudor stainless steel bracelet and clasp. With Certificate of Authenticity, Tudor International Guarantee card dated 07/08/2019 and Tudor box. Balance of 5 year Tudor manufacturer warranty applies. (Pre-owned)