Hippocampus is the seahorse genus. On a watch, it means the Seamaster logo on the crown and caseback. Co-Axial is Omega's escapement design. Master Chronometer is a certification issued by METAS, the Swiss Federal Institute of Metrology. A watch sold as a first copy can carry the seahorse, the words Co-Axial, and the words Master Chronometer. It does not carry the certification. METAS tests the finished watch, and each pass gets one number.

What the Three Words Mean

Hippocampus

The seahorse marks the Omega Seamaster family. It sits on the crown, the caseback, and some dials. It is a logo. It states nothing about the movement, the case material, or the accuracy.

Co-Axial

The Co-Axial escapement uses three pallet jewels. A standard lever escapement uses two. The third jewel cuts sliding contact between the pallet stones and the escape wheel. Omega put the design into series production in 1999. It sits inside the movement. You cannot see it through the caseback on most models.

Master Chronometer

METAS runs eight tests on the cased watch, not on a loose movement. Daily rate must stay between 0 and +5 seconds. The watch runs in a 15,000 gauss field during part of the test. Water resistance and power reserve are measured. This is a level above COSC, which tests movements only and allows -4 to +6 seconds per day.

Numbers on a Real Seamaster Aqua Terra

  • Caliber 8900 or 8800, automatic, 39 jewels.
  • 25,200 vibrations per hour, 3.5 Hz.
  • Power reserve 60 hours.
  • Silicon balance spring. Omega calls it Si14.
  • Magnetic resistance to 15,000 gauss, 1.5 tesla.
  • A METAS card with a certification number.

What a First Copy Does Not Have

  • No Co-Axial escapement. Most copies use a standard lever escapement.
  • No silicon balance spring. Steel hairsprings magnetize.
  • No METAS number that resolves in the METAS database.
  • No magnetic test result. A 1,000 gauss magnet can stop a copy.
  • Stamped or printed caseback art in place of relief work.

Checks Before You Buy

  1. Ask for the certification number and the reference. The number has eight digits.
  2. Look the number up in the METAS database. One number maps to one watch.
  3. Ask for a timegrapher photo with a full wind, dial up. Rate should read 0 to +5 seconds per day.
  4. Read the beat rate. A reading of 28,800 vph does not match the 8900.
  5. Compare case diameter, thickness, and weight with Omega's published figures.

US Law

18 U.S.C. 2320 makes trafficking in counterfeit goods a federal offense. US Customs can seize shipments. Terms like first copy, master quality, and AAA are seller terms. They are not factory grades and not certifications.

If a listing cannot show a METAS number that resolves, the watch is not a Master Chronometer. That is the one test with a public record.