Short answer
217.10.41.21.03.004 does not exist in the Omega catalog. Omega has no published reference with that number. It is a replica-market label written to imitate Omega's reference format. The digits describe a 41 mm stainless steel case with a blue dial. "Hippocampus" points to the seahorse emblem Omega stamps on Seamaster casebacks. The watch being copied is a 41 mm Seamaster Aqua Terra style model.
How the number is built
Omega writes references as six groups of digits: case and bracelet code, material, case size, movement family, dial color, version. Replica listings reuse that pattern and put a factory code in the first group.
- 217: factory or case-family code used by the seller. Omega's three-digit codes in this position map to specific case and bracelet sets.
- 10: stainless steel in Omega's scheme.
- 41: case diameter in millimeters.
- 21: movement family code. In this replica number it is a label, not proof of a caliber.
- 03: blue dial.
- 004: version number. The Omega original in this size and dial color carries a different final group.
The hippocampus mark
Omega placed the seahorse, or hippocampus, on Seamaster casebacks from the mid-1950s. The emblem sits in a caseback medallion and shows a horse with a fish tail. It is a registered trademark, not decoration. A replica that copies it copies a protected mark.
What the original watch is
A 41 mm Seamaster Aqua Terra with a blue dial, a date window, and a steel bracelet. Water resistance is 150 m. The crystal is sapphire with an anti-reflective coating. The movement is the Master Chronometer caliber 8900, which runs at 25,200 vibrations per hour and uses a co-axial escapement. Retail sits at about 5,000 to 6,500 USD depending on year and bracelet.
What replica versions ship with
Three movement types show up in this size class.
- Miyota 8215 or 9015. Japanese, 21,600 vibrations per hour. The 8215 does not hack.
- Seagull ST21 or an ETA 2824 clone. 28,800 vibrations per hour.
- A decorated copy marked 8900. It is a standard three-hand movement with a printed rotor. It has no co-axial escapement.
Case thickness on replicas runs 12 to 14 mm. The original measures about 13.2 mm. Water resistance figures in replica listings are not tested by any third party.
Checks before you compare two units
- Measure the case with calipers. A true 41 mm case reads 41.0.
- Check lug width. The 41 mm Aqua Terra uses 20 mm lugs.
- Look at the crystal edge for the sapphire bevel.
- Inspect caseback engraving under magnification. Laser etching on replicas is shallow and uneven.
- Ask for a timegrapher reading. Rate and beat error are measurable. Seller claims are not.
Legal facts
Counterfeit watches carry marks owned by Omega and its parent group, Swatch Group. Selling them is trademark infringement. In the United States, trafficking in counterfeit goods is a criminal offense under 18 U.S.C. 2320, and 19 U.S.C. 1526 covers seizure and forfeiture at import. U.S. Customs and Border Protection seizes counterfeit watches at ports. Shipments addressed to buyers can be detained or destroyed. EU customs rules allow the same treatment for goods held at borders.
Open questions
No public data ties factory code 217 to one workshop. Batch quality inside the same reference varies between sellers who list the same string. No third-party lab test of water resistance for this reference exists.