This watch is unusual in that the dial is not signed ?Officially Certified Chronometer? . The case back of this watch bears two reference numbers. The first 6565 corresponds to the reference number which this series of references is based on. The second 6552 which corresponds to the number between the lugs is for this specific model. The caliber 1030 was produced between 1950 and 1957 and continued to be found in watches for some years later. This watch is illustrated in ?Rolex Collecting Wristwatches? by Osvaldo Patrizzi 2001 Edition p. 184.