The Fifty Fathoms, in the colour of the water.

The 1953 original was black, because a black dial with luminous markers is what a diver reads in murky water. Blancpain added the blue when it revived the line, and the blue is the same dial and bezel construction in a different colour: a sunburst dial that goes from bright to navy as the light moves, and a sapphire bezel insert that reads as a glass ring rather than a painted one. The luminous numerals and darts are the same cream on both.

Underneath is the 1315, three barrels for five days of reserve and a silicon balance spring, and the 300-metre case with its screw-down crown. The sail-canvas strap is the strap the revival launched on; the model row’s NATO suffix means the seller may ship the nylon version instead, which is the question to ask.

This is a regular Amazon listing from a marketplace seller with Amazon’s 30-day return window; it is not a Luxury Stores unit and the seller has not published a condition. The second button opens the live search for blue Fifty Fathoms in case this one has sold.

Fifty Fathoms have resold for under new and close to what pre-owned buyers paid, sometimes more, sometimes less; that is a pattern, not a promise, and nothing here is investment advice.