ROLEX. A MENS EXTREMELY RARE STAINLESS STEEL AUTOMATIC "RAIL DIAL"  BRACELET WATCH Model: Sea Dweller "Rail Dial" Reference number: 1665 Date: 1978 Movement: Signed, 26-Jewels, Cal.1570, adjusted on 5 positions and temperatures, automatic No. D87xxxx Dial: Signed, matte black, luminous dot hour markers and baton quarters, white outer minute divisions, polished mercedes hands with luminous insert, centre seconds hand, date aperture at the 3 o'clock position Case: Signed, brushed and polished, screw down Oyster back, shouldered crown, helium valve at the 9 o'clock position, bidirectional bezel with black bezel insert, No.571xxxx Bracelet: Signed, brushed and polished stainless steel Oyster link 93150, signed deployment clasp  Size: 38mm Accompaniments: Rolex box, Rolex papers dated 1980 The ‘Rolex Sea Dweller’ was created in 1967 and is characterised by the two lines of red text that are see on the dial. This interesting detail attracted the nickname of ‘The Double Red Sea Dweller’ shortly after its release in 1971. Unlike the more common Rolex Submariner, this watch can be distinguished by its thicker case, flush helium escape valve, domed glass and plain crystal in place of the Submariner’s familiar cyclops lens for date aperture magnification. Capable of operating at depths of up to 610 meters, it enabled divers at the time to work deeper than ever before. These early model evolutions were all ref:1665 and could be chronologically identified from their Mark 0, Mark 1, Mark 2, Mark 3 or Mark 4 designations. However, they are typically referred to using their more familiar descriptive names, such as ‘Double Red’ and ‘Great White’. The Great White’s main differentiating features include the replacement  of the ‘Submariner’ tag with white lettering on the dial, varying layout designs for the different models and that the  ‘Sea-Dweller’ lettering is no longer crimson. The case-back of the 1665 was also modified so that the engraving curved uniquely follow the lines of the outer-case. The main characteristic of the Mark 2 (as described above?) dial, also known as the ‘Rail Dial’, is  the dial text of ‘Sea-Dweller’ and ‘2000ft=610m’ are perfectly aligned, the ‘ft’ and the ‘m’ are in italics, and the title letter of ‘Certified’ is in line with that of ‘Chronograph’ in the previous line. The famous and highly sought after ‘COMEX’ derivative used exactly the same dial, with ‘Sea Dweller’ substituted for the company name. Another notable feature can be found towards the base of the dial at 6 o'clock, which reads ‘T SWISS T<25’, denoting that the watch is Swiss and contains a certain quantity of tritium that emits less than 227 MBq. Previous models are instead inscribed ‘SWISS-T< 25’, denoting that the watch is Swiss but that this watch contains a certain quantity of tritium that emits less than 925 MBq.  These features all culminate to render the ‘Rolex Sea Dweller-Rail Dial’ a rare and unique model, making it a particularly sought after piece for collectors. As with all vintage Rolexes, condition and originality play as big a part as rarity in determining their potential value. Finding an untouched watch that is not only ‘one owner from new’, but also fresh to the market, makes this watch exceptionally special.