Seamaster 120M Automatic 36.25 Yellow Gold / Diamond / Blue

In Context

At 36.25 mm it is classically proportioned: the size a dress watch was understood to be for most of the twentieth century, and small enough to sit under a cuff. The case back is closed, so the movement stays out of sight, and the sapphire crystal will resist everything short of deliberate abuse. 120 m is genuine swimming resistance — more than the shape of this watch suggests it would need.

The movement winds itself from the motion of your wrist. 44 hours of reserve carries it overnight, but not through a weekend in a drawer. At 28,800 vph the seconds hand advances 8 times a second.

2105.81.00 stands on its own in this catalogue — no other reference here shares its base number. It pairs a blue dial with a yellow gold case.

The 1109 is Omega's ETA 2892-A2 of the early 1990s, the non-chronometer automatic of the mid-size Seamaster. It powers 19 watches in this library. The 2892 is the thin automatic the [2892 piece](/blog/the-eta-2892) describes, and the 1109 is that base with Omega's finishing, 21 jewels, a 44-hour reserve and a beat of 28,800 vph at 25.6 mm across. The [1120](/calibers/omega-1120) that followed is the same movement adjusted and certified as a chronometer, with two more jewels, and the two ran side by side in the Seamaster of the 1990s. In the library it powers 11 [Seamaster 120M](/brands/omega/seamaster-120m) references at 36.25 mm, most of them in yellow gold, and 8 [Seamaster Diver 300M](/brands/omega/seamaster-diver-300m) mid-size references. The [2500](/calibers/omega-2500) is the co-axial movement Omega later built on the same base.

18 other watches in the library run the Omega 1109.

Omega

Seamaster Diver 300M Automatic 36.25 Stainless Steel / White / Bracelet

2552.20.00 · 36.25 mm

Omega

Seamaster Diver 300M Automatic 36.25 Stainless Steel / Yellow Gold / Blue / Bracelet

2452.80.00 · 36.25 mm

Omega

Seamaster Diver 300M Automatic 41 Stainless Steel / Yellow Gold / White / Bracelet

2432.20.00 · 41 mm

Omega

Seamaster Diver 300M Automatic 36.25 Yellow Gold / White / Bracelet

2151.20.00 · 36.25 mm