Rolex. An extremely rare and unusual stainless steel self-winding water-resistant wristwatch with sweep centre seconds, date, 24 hour hand, bracelet and prototype "bicchierini" dial

It is understood that the present watch is the only reference 16550 featuring a so-called "bicchierini"-dial and represents a significant addition to scholarship regarding the history and development of Rolex's celebrated Explorer II.

No other Explorer II reference 16550 model was ever made with such a dark grey matte dial featuring the luminous hour markers enclosed by a small, raised white gold frame. This layout consequently renders the luminous centre less obvious, a feature introduced by Rolex for their GMT-Master and Submariner models in the 1980s. The Explorer models of reference 16550 are to date only known to exist with the luminous material enclosed by a thin white gold frame of large size and different shape.

According to research, Rolex made a special request to one of their dial suppliers, Beyeler, for the Basle Watch Fair in 1982, ordering two such dials for the Explorer II reference 16550. It is today known that this dial design was never chosen to go into regular production and these two prototypes have remained the only examples of this design. After the fair only one of these dials was mounted on a watch - serial number 8399062, the present watch, which was later sold to Rolex New York in 1984.

Amongst collectors, such dial design is also referred to as the "nipple dial".