Rolex Explorer II White "Porcelain" Dial Ref. 16550Some things get better with time, like wines, whiskey, cheesesand many watches that carry Tritium lume! The 16550 was a transitional model produced between the reference 1655 and its successor, the 16570. Manufactured for about five years, from 1984 to 1989, it was the first Explorer II to feature an independently adjustable GMT hand, which could be set without stopping the movement. We love these white dialed 16550s, as they sometimes age with grace.