Make:Rolex Model: Unicorn Caliber:636 Movement: Aegler Rebberg movement 15 jewels unicorn Number:511 Case material: silver marked Wilsdorf & Davis W&D sponsor's mark Case size: 27mm excluding crown Case size from lugs to lugs: 33mm Strap:genuine calf leather 18-20 cm Rolex had a number of subsidiary brand names in the 1920s and 30s to be used on their cheaper lines of watches including Unicorn, Marconi, and Rolco. All of the subsidiary brands were dropped at the end of WWII and Tudor was launched as the name for their entry level lines. Watch serviced and keeps time well Vintage box included Will ship insured and register