The ‘Choco-line’ Grené Rolex. A very rare and early stainless steel chronograph wristwatch with brown registers, "underline double Swiss" dial and bezel calibrated for 300 units, Cosmograph, ref. 6239, manufactured in 1963. Estimate: SFr.40,000-80,000 (US$40,000-80,000). Sold for $296,250.