Speedmaster HB-SIA Co-Axial GMT Titanium / Black Carbon / Rubber

In Context

At 44.25 mm it is a large watch — well above this catalogue’s 40 mm median, and enough to dominate a narrow wrist. The case back is closed, so the movement stays out of sight, and the sapphire crystal will resist everything short of deliberate abuse. 100 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. 55 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.

321.92.44.52.01.001 stands on its own in this catalogue — no other reference here shares its base number. It pairs a black dial with a titanium case. Introduced in 2008. Beyond the time it carries a chronograph and a gmt.

The 3603 is the GMT version of Omega's Piguet-based chronograph: the 1285 architecture with a second time zone, in the 44 mm chronographs of the 2000s. It powers 18 watches in this library. The 1285 is the thin column-wheel chronograph the [Piguet piece](/blog/the-frederic-piguet-1185-the-thin-chronograph-under-three-maisons) traces, and the 3603 adds a 24-hour hand to it, with 37 jewels, a 55-hour reserve and a beat of 28,800 vph, certified by the COSC. Every reference here is 44 mm or 44.25 mm, the size the extra module asked for. In the library it powers 6 [Aqua Terra](/brands/omega/aqua-terra) Chronograph GMTs, 4 [Speedmaster Broad Arrow](/brands/omega/speedmaster-broad-arrow) GMTs at 44.25 mm, 3 [De Ville](/brands/omega/de-ville) Chronoscope GMTs, 3 [Speedmasters](/brands/omega/speedmaster-automatic-quartz) and 2 [Seamaster Diver 300M](/brands/omega/seamaster-diver-300m) GMT chronographs. The [3313](/calibers/omega-3313) is the co-axial version of the same base without the GMT, and the [3612](/calibers/omega-3612) the split-seconds version; the glossary defines the [GMT](/glossary/gmt) display.

17 other watches in the library run the Omega 3603.

Omega

Seamaster Aqua Terra 150M Co-Axial 44 GMT Chronograph Stainless Steel / Silver

231.13.44.52.04.001 · 44 mm

Omega

Speedmaster HB-SIA Co-Axial GMT Titanium / Black Carbon / Bracelet

321.90.44.52.01.001 · 44.25 mm

Omega

Speedmaster Broad Arrow Co-Axial GMT Stainless Steel / Black / Bracelet

3581.50.00 · 44.25 mm

Omega

Speedmaster Broad Arrow Co-Axial GMT Stainless Steel / White

3881.30.37 · 44.25 mm