This watch is unusual due to its excellent original un-restored condition with unusual engine-turned hooded lugs. It is also accompanied by the original rating certificate showing that it was timed in 5 positions and at 3 temperatures. The caliber 9 3/4??? Ref. 620 was produced between 1940 and 1951. This watch is illustrated in ?Rolex Collecting Wristwatches? by Osvaldo Patrizzi 2001 Edition pp. 164 165.