The short answer
"323" is not an Omega reference. Real Aqua Terra case numbers look like 220.10.41.21.03.001, and the three-digit "323" turns up as a listing tag on marketplace and forum threads where sellers group a batch of dials or cases. So the question worth answering is narrower: is the Aqua Terra in front of you genuine? No photo settles that. The movement, the caseback, and the paperwork do.
Why this model is hard to copy well
On current Aqua Terra models the movement is the whole point. Calibres 8900, 8800, and 8901 are Master Chronometer certified, meaning METAS tests the finished watch rather than the movement alone. That covers magnetic resistance to 15,000 gauss, rate in several positions, and power reserve. Replicas drop in a Miyota 9015 or a Seagull ST21, then hide it under a decorated plate. The rotor engraving sits flat, the fonts run heavy, and winding feels thin compared with the real Co-Axial.
Checks that separate them
- Case: the twisted lugs should be polished on the top facet and brushed on the flank, with a hard line between. Copies round that edge.
- Dial: teak deck grooves are cut clean and even, and the applied logo sits flat with sharp edges. Fakes show soft grooves and a logo standing proud of the dial.
- Hands: brushed and polished facets catch light on one side only. On copies both sides flash.
- Crystal: anti-reflective coating goes on the inside. If the outer surface throws purple or blue, stop.
- Caseback: the eight-digit serial is engraved, not printed, and it matches the number on the movement.
The paperwork test
Every Master Chronometer watch leaves the factory with a certification card carrying a unique code, plus pictograms and warranty cards. That code can be verified with Omega. Boxes get copied well these days. Cards do not, and a seller who claims the card was lost is usually telling you something.
Buying, and what to do if you get burned
Buy from an Omega boutique, an authorized dealer, or a grey dealer who allows returns and lets you have the watch inspected. An independent watchmaker who services Omega can confirm a movement in minutes. If a watch turns out to be counterfeit, dispute the charge with your card issuer, report the seller to the brand's anti-counterfeiting team and to the FTC, and know that U.S. Customs can seize counterfeit imports. Importing or selling one is a federal matter, not a gray area, and the buyer carries most of the risk.