Seamaster Planet Ocean 600M Co-Axial 45.5 Master Chronometer Chronograph Stainless Steel / Grey / Bracelet

In Context

At 45.5 mm it is a large watch — well above this catalogue’s 40 mm median, and enough to dominate a narrow wrist. At 18.87 mm it is very tall, and sits high off the wrist. The case back is open, so the movement is visible without taking the watch apart, and the sapphire crystal will resist everything short of deliberate abuse. 600 m is a professional diving rating, far past any demand a wrist is likely to make of it.

The movement winds itself from the motion of your wrist. 60 hours of reserve is enough to set it down on Friday evening and find it still running on Monday. At 28,800 vph the seconds hand advances 8 times a second.

215.30.46.51.99.001 stands on its own in this catalogue — no other reference here shares its base number. It pairs a grey dial with a stainless steel case. Beyond the time it carries a chronograph.

The 9900 is the Master Chronometer version of Omega's in-house chronograph, introduced in the Planet Ocean 600M Chronograph in 2016. It powers 44 watches in this library. It keeps the [9300](/calibers/omega-9300)'s architecture, a column wheel, a vertical clutch, two barrels for 60 hours at 28,800 vph and the combined 12-hour and 60-minute counter at 3 o'clock, and adds the METAS specification: a silicon balance spring on a free-sprung balance, non-magnetic alloys and certification of the cased watch to 15,000 gauss. It is 32.5 mm across with 54 jewels. The 9901 is the version with a gold rotor and bridges, and the [9904](/calibers/omega-9904) adds a moon phase. In the library it sits under 19 [Planet Ocean](/brands/omega/seamaster-planet-ocean) chronographs at 45.5 mm, 10 [Seamaster Diver 300M](/brands/omega/seamaster-diver-300m) chronographs at 44 mm, 9 [Speedmaster](/brands/omega/speedmaster-automatic-quartz) Racing Master Chronometers at 44.25 mm, 4 [Dark Side of the Moons](/brands/omega/speedmaster-dark-side-of-the-moon) and 2 Speedmaster Pilots. The 45.5 mm case accounts for 19 references and the 44.25 mm for 13. The [3861](/calibers/omega-3861) is the hand-wound Master Chronometer chronograph of the Moonwatch, and the [8900](/calibers/omega-8900) the three-hand movement of the same certification.

43 other watches in the library run the Omega 9900.

Omega

Seamaster Diver 300M Master Co-Axial 44 Chronograph Stainless Steel / Blue / Bracelet

210.30.44.51.03.001 · 44 mm

Omega

Seamaster Diver 300M Master Co-Axial 44 Chronograph Stainless Steel / Sedna Gold / Black / Bracelet

210.20.44.51.01.001 · 44 mm

Omega

Seamaster Diver 300M Master Co-Axial 44 Chronograph Stainless Steel / Black / Rubber

210.32.44.51.01.001 · 44 mm

Omega

Speedmaster Racing Master Co-Axial Stainless Steel / Black / Bracelet

329.30.44.51.01.001 · 44.25 mm