Seamaster PloProf Co-Axial Stainless Steel / Black / Shark

In Context

At 55 mm this is exceptionally large for something worn on a wrist, closer to a pocket watch given lugs. The case back is closed, so the movement stays out of sight, and the sapphire crystal will resist everything short of deliberate abuse. 1200 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 25,200 vph the seconds hand advances 7 times a second.

224.30.55.21.01.001 stands on its own in this catalogue — no other reference here shares its base number. It pairs a black dial with a stainless steel case.

The 8500 is the first movement Omega designed from scratch around the co-axial escapement, introduced in the De Ville Hour Vision in 2007. It powers 167 watches in this library. Until then the escapement had lived on an ETA base, the [2500](/calibers/omega-2500). The 8500 was built for it: two barrels mounted in series for a 60-hour reserve, a free-sprung balance, bidirectional winding, 39 jewels, a 29 mm diameter and a beat of 25,200 vph chosen for the escapement rather than inherited. From 2011 it received the Si14 silicon balance spring, and later an anti-magnetic version carried the Master Co-Axial name. It is the ancestor of every current Omega automatic: the [8900](/calibers/omega-8900) is its Master Chronometer successor and the [8800](/calibers/omega-8800) its smaller derivative. In the library it sits under 81 [Aqua Terras](/brands/omega/aqua-terra), the 38.5 mm and 41.5 mm teak-dial models of 2008 to 2017, 38 [Constellations](/brands/omega/constellation), 31 [Planet Oceans](/brands/omega/seamaster-planet-ocean) of the 2011 generation, 11 [De Villes](/brands/omega/de-ville) and 6 [Ploprofs](/brands/omega/seamaster-ploprof). Cases run from 38 mm to 55 mm, with 38.5 mm the most common at 51 references. The [8501](/calibers/omega-8501) is the same movement with a gold rotor for gold cases, the [8520](/calibers/omega-8520) the smaller version for ladies' watches, and the [8601](/calibers/omega-8601) the annual calendar built on it.

166 other watches in the library run the Omega 8500.

Omega

Seamaster Aqua Terra 150M Co-Axial 38.5 Stainless Steel / Yellow Gold / MOP

231.23.39.21.55.002 · 38.5 mm

Omega

Seamaster Aqua Terra 150M Co-Axial 41.5 Stainless Steel / Silver

231.13.42.21.02.001 · 41.5 mm

Omega

Seamaster Aqua Terra 150M Co-Axial 38.5 Stainless Steel / Black

231.13.39.21.01.001 · 38.5 mm

Omega

Seamaster Aqua Terra 150M Co-Axial 38.5 Stainless Steel / Red Gold / MOP

231.23.39.21.55.001 · 38.5 mm