The short answer
"Hippocampus" is the seahorse stamped on the caseback of Omega Seamaster watches. The mark has appeared on Seamaster casebacks since 1957. A "replica hippocampus 2010" is a copy built to look like a Seamaster Omega sold in 2010. The term covers the Seamaster Diver 300M, the Planet Ocean 600M, and the Aqua Terra. Copies of these models are made in China and sold through online shops. They are not Omega products and carry no Omega warranty or service.
Seamaster models sold in 2010
- Seamaster Diver 300M, 41 mm steel case, calibre 2500 Co-Axial, ref 212.30.41.20.01.003 and nearby numbers.
- Seamaster Planet Ocean 600M, 42 mm ref 2201.50.00 and 45.5 mm ref 2200.50.00, calibre 2500.
- Planet Ocean Liquidmetal Limited Edition, 2010, 1948 pieces, ceramic dial with a Liquidmetal bezel insert.
- Seamaster Aqua Terra 150M, steel and two-tone, 38.5 mm and 41 mm cases.
Shared details on the 2010 line: a helium escape valve at 10 o'clock on the diver and Planet Ocean, a wave-pattern dial on the Diver 300M, and a caseback with the hippocampus medallion plus the word Seamaster.
How 2010-era copies differ
Most copies from that period used an ETA 2824-2 clone or a Sea-Gull ST2130. Both beat at 28,800 vibrations per hour. The Omega calibre 2500 beats at 25,200. A timegrapher shows the gap.
Other points of difference: the shape of the bezel pearl, the date font and date window position, the depth of the caseback seahorse engraving, and the helium escape valve, which on most copies does not open. Case thickness on copies often ran 0.5 mm to 1 mm above the genuine Planet Ocean range of 14.2 mm to 15 mm.
No public data exists on production totals for these copies. Sales figures quoted by sellers cannot be checked against any registry.
Legal status in the United States
Trafficking in counterfeit goods is a federal crime under 18 U.S.C. Section 2320. A first offense carries up to 10 years in prison and a $2 million fine for an individual. Civil claims fall under the Lanham Act, 15 U.S.C. Section 1114. U.S. Customs and Border Protection may seize shipments that carry a counterfeit mark. One narrow rule allows a single item of each type brought in personal baggage for personal use, not for resale.
Buyers also report non-delivery and card fraud from replica sites. That risk does not depend on the watch model.