The reference 1802 is the reference number that refers to the specific characteristics of this watch the reference 1803 is the identical watch from the same series but with a polished and brushed case and faceted bezel. The case bodies and backs are interchangeable and it was quite usual for watches to leave the factory with different references on the body and back from within the same series. For a note see lot 290. This watch is illustrated in ?Rolex Collecting Wristwatches? by Osvaldo Patrizzi 2001 Edition p. 270.