The Sea-Dweller 16660 ‘Triple Six’ was the first Sea-Dweller to be fitted with a sapphire glass. The first series used matte dials (divided in Mark 1 and Mark 2 variants) while the second series used the newer gloss dials. It was replaced by the 16600 in 1988. The present watch has a Mark 1 matte dial, most easily identified by the base of the ‘F’ in ‘Feet’ reaching to the ‘E’ of ‘Superlative’. On the Mark 2, the base reaches to the ‘V’.
