OMEGA · Seamaster Aqua Terra 150M and Seamaster Railmaster
OMEGA 220.10.41.21.01.002 vs OMEGA 235.10.38.20.06.001
10 published specifications differ between these two, and 4 are identical. Every figure below is what the manufacturer states for that reference; nothing is inferred from the other watch.
What differs
| Specification | OMEGA Aqua Terra 150M 41mm, black dial220.10.41.21.01.002 | OMEGA Railmaster Co-Axial Master Chronometer 38mm, grey dial235.10.38.20.06.001 |
|---|---|---|
| Case | Steel, 41 mm | Steel, 38 mm |
| Diameter | 41 mm | 38 mm |
| Thickness | 13.4 mm | 12.36 mm |
| Lug to lug | 48 mm | 44.92 mm |
| Lug width | 20 mm | 19 mm |
| Dial | Black | Grey |
| Calibre | Calibre OMEGA 8900 | Omega 8806 |
| Movement | Self-winding movement with Co-Axial escapement, automatic winding in both directions | Self winding |
| Power reserve | 60 hours | 55 hours |
| Movement notes | Resistant to magnetic fields reaching 15,000 gauss. Free sprung-balance with silicon balance spring, two barrels mounted in series, and a time zone function. Rhodium-plated rotor and bridges with Geneva waves. Total product weight approximately 148 g. | Listed by OMEGA as a Master Chronometer certified watch. Total product weight approximately 136 g. |
What is identical
Worth knowing as much as the differences: these are the specifications you cannot use to tell the two apart.
- Water resistance
- 15 bar (150 metres / 500 feet)
- Crystal
- Domed scratch-resistant sapphire crystal with anti-reflective treatment on both sides
- Bracelet
- Steel
- Clasp
- Foldover butterfly clasp with comfort setting
Stated for one, not the other
These rows cannot be compared, because one maker publishes the figure and the other does not. An empty cell is a gap in the manufacturer's documentation, not a gap in the watch — and not a licence to fill it in from the other column.
| Certification | Master Chronometer, approved by METAS | not stated |
|---|
What the differences cost you
Each note below follows from the published figures in the tables above — what they mean for intake, for a listing, and for the handover. Nothing here estimates a price or a margin.
One of these is the harder fit
Lug to lug is 48 mm on the 220.10.41.21.01.002 against 44.9 mm on the 235.10.38.20.06.001 — a 3.1 mm difference across the wrist. Diameter is what buyers ask about; lug to lug is what decides whether a case sits flat or overhangs. Ask for a wrist measurement before shipping the 220.10.41.21.01.002, and put the figure in the listing rather than the diameter alone.
These reach different buyers
41 mm on the 220.10.41.21.01.002 against 38 mm on the 235.10.38.20.06.001. Diameter is a poor predictor of how a watch actually sits, but it is the field buyers filter on, so the two land in front of different people. Do not let one listing's photographs or copy stand in for the other.
Different movements to verify and to service
The 220.10.41.21.01.002 runs the Calibre OMEGA 8900 and the 235.10.38.20.06.001 the Omega 8806. Two consequences at intake: the service history that is normal for one calibre is not evidence about the other, and the calibre is the check that catches a movement swapped into the wrong case. Confirm the movement matches the reference rather than assuming it from the dial.
What to check on each
220.10.41.21.01.002
- Test the time zone function properly: the hour hand should jump independently in one-hour steps without disturbing the minutes or seconds. A hand that drags the minute hand with it is a fault, not a quirk.
- Check the anti-reflective coating on both crystal surfaces. OMEGA specifies treatment on both sides, and worn or patchy coating on the inner face cannot be polished away — it needs a new crystal.
- Wind and run it for a full day to confirm the 60-hour reserve behaves. Twin barrels in series should deliver consistent amplitude rather than fading early.
235.10.38.20.06.001
- Quote the 44.92 mm lug to lug. It is under forty-five millimetres, which makes this the easiest OMEGA here to fit on a small wrist and is the strongest selling point the sheet contains.
- Check the lug width is the published 19 mm before sourcing a strap. Nineteen is a stocked but uncommon size and a buyer will assume twenty.
- Confirm the calibre is the 8806, which appears on no other OMEGA documented here and carries 55 hours rather than the 60 of the 89xx movements.
Sources
- OMEGA official product page for reference 220.10.41.21.01.002 (Seamaster Aqua Terra 150M Co-Axial Master Chronometer 41 mm; steel) - Case: steel; 41 mm; Dial color: black; Crystal: domed scratch-resistant sapphire crystal with anti-reflective treatment on both sides; Water resistance: 15 bar (150 metres / 500 feet); Movement: Calibre OMEGA 8900; self-winding movement with Co-Axial escapement; certified Master Chronometer approved by METAS; resistant to magnetic fields reaching 15000 gauss; free sprung-balance with silicon balance spring; two barrels mounted in series; automatic winding in both directions; time zone function; special luxury finish with rhodium-plated rotor and bridges with Geneva waves; Power reserve: 60 hours; listed with a 5-year warranty; Re-read 2026-09-23, the page additionally publishes: Between lugs: 20 mm; Lug-to-lug: 48.00 mm; Thickness: 13.40 mm; Case diameter: 41 mm; Total product weight (approx.): 148 g; Type of Clasp: Foldover butterfly clasp with comfort setting; Bracelet material: Steel — retrieved 2026-09-23
- OMEGA official product page for reference 235.10.38.20.06.001 (Seamaster Railmaster Co-Axial Master Chronometer 38 mm, steel) - Between lugs: 19 mm; Lug-to-lug: 44.92 mm; Thickness: 12.36 mm; Case diameter: 38 mm; Case: Steel; Dial color: Grey; Crystal: Domed scratch-resistant sapphire crystal with anti-reflective treatment on both sides; Water resistance: 15 bar (150 metres / 500 feet); Total product weight (approx.): 136 g; Caliber: Omega 8806; Movement type: Self winding; Power reserve: 55 hours; Bracelet material: Steel; Type of Clasp: Foldover butterfly clasp with comfort setting — retrieved 2026-09-23
Not affiliated with OMEGA. Specifications are read from each manufacturer's own published documentation on the dates shown and may change; the manufacturer's current documentation governs.