Rolex Explorer, Ref 1655 in Stainless steel, Circa 1975

In 1971, Rolex expanded their Explorer line of watches with the release of the reference 1655. Rather than simply being a revised version of the existing Explorer watch, the reference 1655 was an entirely different timepiece; and as such, was given the “Explorer II” designation. Instead of replacing the existing Explorer, the reference 1655 Explorer II was to be offered alongside the traditional, time-only Explorer watch as a complementary offering within the Rolex catalogue.