Rolex Zenith Daytona ref 16518 an 18ct gold automatic chronograph wristwatch with inverted 6 dial, circa 1991. Dial: white. Calibre: cal. 4030 automatic, 31 jewels. Movement number: 48779. Case: 18ct gold, screw-down back. Case number: N231365. Closure: 18ct gold Rolex folding clasp. Dimensions: 40 mm. Signed: case, dial and movement. Accessories: none. The present Rolex Daytona 16518 contains the much celebrated calibre 4030 based on the Zenith El Primero movement. This reference can instantly be identified by looking at the dial. The so-called 'inverted 6' dials were only in production for a very limited amount of time, where the Arabic marker at 6 on the 12 hour recording subsidiary dial appears to be upside down, adding to the interest of the watch.