OMEGA Planet Ocean 600M 217.30.42.21.01.001: specs and checks

A flat crystal, coated on both sides

Most of the OMEGA references documented here carry a domed crystal. This one is specified as flat, with anti-reflective treatment on both sides.

Both halves of that matter at a viewing.

Flat means the glass sits closer to the case and presents an even plane rather than a curve. It does not catch light the way a dome does, which makes surface damage easier to see — a small mercy when grading.

Both sides means there is an outer coating here. Several OMEGA references specify treatment inside only, and on those the outside is bare sapphire: effectively unscratchable. An external coating is not. It can be scuffed, worn thin at the edges, and marked by a careless polish.

So inspect this crystal twice. Once looking through it for interior haze that cannot be reached, and once looking at it under raking light for patchiness or wear in the outer layer. The two faults look nothing alike and have different costs.

The extension nobody has ever opened

The clasp is a foldover clasp with comfort setting and diver extension — three mechanisms in one assembly.

The diver extension is the one to pay attention to. Its job is to add length so the band can close around a neoprene sleeve, and on the overwhelming majority of these watches it has stayed folded since the day it left the boutique.

Open it fully. Check the hinge has not sprung, that nothing binds, and that it closes flat again rather than standing proud. Then confirm its catch actually holds rather than simply resting shut.

The comfort setting is separate: a small micro-adjustment with detents. Run it through its travel and back, feeling for positions that no longer click.

At 177 g — heavier than every OMEGA documented here apart from the Diver 300M and the Ultra Deep — all of this is carrying real weight.

Sixty bar, and what it is not

OMEGA publishes 60 bar (600 metres / 2000 feet).

That is double the rating of the two Seamasters documented here at 300 metres, and it is a genuine engineering difference: a thicker case band, a thicker crystal, and a deeper helium-era heritage behind the design.

It is also, on a used watch, a factory figure and nothing more. Gaskets harden. A case that has been opened has been resealed by somebody whose work you cannot inspect. Nobody has pressure tested the example on your bench.

Say so. Quote the specification as a specification, and either test it or state plainly that it has not been tested. Both are honest; repeating "600 metres" as if it were a measurement is not.

The calibre that spans the range

The movement is the calibre 8912, self winding, 60 hours — the same movement OMEGA specifies for the Seamaster 300 at 300 metres and for the 6000-metre Ultra Deep.

One calibre, three depth ratings spanning a factor of twenty. That is a useful thing to understand: the movement tells you almost nothing about the case around it, and the case is where the depth rating lives.

Published dimensions: 42 mm across, 13.79 mm thick, 47.50 mm lug to lug, 21 mm between the lugs.