With Rolex period "Compagie Maritime d'Expertise" sales tag.
Between the late 1960s and the early 1980s, roughly 300 examples of the Sea-Dweller reference 1665 fitted with a gas escape valve were supplied to COMEX (Compagnie Maritime d'Expertise) in Marseille, a professional diving operation for the oil industry. The model was never available to the public.
Worn under sometimes extreme conditions (for which it was actually made for), a number of these watches have not survived, others have been repeatedly serviced, sometimes not with period or correct exchanged parts.
The present COMEX Sea-Dweller reference 1665 is one of the exceedingly rare examples of this model preserved in excellent overall condition. It impresses with a number of details considered treasures by the demanding collector, such as its so-called “rail” dial. Its name is derived from the symmetric division of the two lines below the centre, "Superlative" and "Officially" to the left, clearly separated by a vertical space (thus "rail"), and "Chronometer" and "Certified" to the right. The case has retained its sharp outlines, crisp milling and last but not least the correct Oyster bracelet for this model, reference 93150.
COMEX reference 1665 is described and illustrated in 100 Superlative Rolex Watches by John Goldberger, pp. 222 & 223.