Rolex Deepsea 136660: specifications and what to check

Four things no other Rolex here has

This reference sits apart from every other Rolex documented on this site, and it does so on four specific published points.

Ringlock System. Rolex names a distinct case architecture for this watch, in addition to the usual monobloc middle case and screw-down back. It is the structural reason the rest of the sheet is possible.

A helium escape valve. A one-way valve on the case side, listed as part of the water resistance specification. It vents helium that has worked into the case during saturation diving, which is the failure mode that otherwise pushes crystals off watches during decompression.

A 5.5 mm crystal. Rolex publishes the thickness, which it does for no other reference here. Five and a half millimetres of domed sapphire is roughly double what a conventional dive watch carries.

3,900 metres. Against 300 on the Submariner, 1,220 on the Sea-Dweller.

Each of those is a thing to look at rather than a thing to repeat. Find the valve. Look at the crystal edge-on. Confirm the case markings match the reference.

The crystal is the exposed part

A domed sapphire 5.5 mm thick stands well above the bezel. That geometry is what lets it resist pressure, and it is also what puts it first in line for every knock the watch takes.

Sapphire does not wear gradually. It stays immaculate and then loses a small bright flake, and on a curved surface that flake is almost invisible looking straight down.

So tip the watch until light rakes along the dome and travel the whole circumference, paying particular attention to where the glass meets the bezel. This is an expensive part, it is specific to the reference, and a chip is not something a photograph will have shown you.

Glidelock, and why it matters most here

The clasp is a folding Oysterlock safety clasp with the Rolex Glidelock extension system — a toothed rail inside the clasp that lets the bracelet lengthen in small increments without tools.

On a watch of this size and mass it is the most-used mechanism on the bracelet, and it is the one that shows wear first.

Run it out to full extension and back in, several times. Each position should engage with a definite click and hold firmly under a pull. A Glidelock that slides under load, or that will not seat in some positions, is worn — and because it sits inside the clasp, nobody ever looks at it until it fails.

Then check the Oysterlock safety catch itself opens and closes positively.

What the depth rating is, and is not

3,900 metres / 12,800 feet is an engineering specification for the case as Rolex builds it.

It is not a statement about the watch on your bench. Seals harden with age. Any case that has come apart was closed again by a hand you never watched. Nothing about this particular watch has been measured.

Quote the figure as a specification, and either have the watch pressure tested or say plainly that it has not been. Both are honest positions. Presenting a factory number as a current measurement is not, and on a watch sold partly on that number it is the claim most worth getting right.

The ordinary parts

Calibre 3235, approximately 70 hours, −2/+2 sec/day after casing, Superlative Chronometer — the same movement Rolex fits to the Sea-Dweller and several 41 mm references.

Bezel is a Cerachrom insert in black ceramic with numerals and graduations coated in platinum: inspect it for chips rather than scratches, and check the platinum coating in the engravings is even and unworn.

The crown is Triplock, three sealing zones rather than Twinlock's two. Thread it and unthread it several times and feel for the catch on the first quarter turn.