Notes: A 1950s automatic chronometer. Found with 18K rose gold or stainless steel cases. The stainless steel cases may or may not have gold bezels.

Mechanism: The 630 was Rolex's second automatic mechanism. The 645 is a variation of the 630 featuring sweep-second and Shock-Resist. It is one of the three size A.260 mechanisms.

Family Notes: In 1926, Hans Wilsdorf introduced the Oyster watch which used a waterproof case, hence the name. He added "Perpetual" to the name when in 1933 he introduced a reliable automatic self-winding watch. Hence the name means "Waterproof, Self-Winding" in Rolex-speak and generally means the watch is water resistant to a depth of 100 meters.