Short answer
A fake Omega De Ville Trésor 18K is a counterfeit watch. The case is gold plate over brass or steel, not solid 18K gold. The movement is a copied or decorated third-party calibre, not Omega calibre 8910. Omega will not service it, and US Customs can seize it. Three checks settle the question: case metal and hallmark, movement and Master Chronometer card, and serial number.
What the genuine watch is
- Case: 18K Sedna gold, yellow gold, or white gold. Sedna is Omega's rose gold alloy with copper and palladium.
- Diameter: 40 mm on most Trésor references.
- Movement: calibre 8910, hand wound, twin barrels, Co-Axial escapement, silicon balance spring.
- Power reserve: 72 hours.
- Certification: Master Chronometer, tested by METAS.
- Magnetic resistance: 15,000 gauss.
- Some references have a solid caseback. Check the reference number against Omega's published specifications before you judge the back.
Check 1: metal and hallmark
18K gold has a density of about 15.5 g/cm3. Stainless steel is about 7.9 g/cm3. A gold Trésor 40 mm on a leather strap weighs more than a steel watch of the same size, and the case head feels dense in the hand. Brass and gold plate are light.
Look at the caseback and the inner faces of the lugs. Swiss gold carries a 750 fineness stamp and a maker's punch. Older pieces also carry the St. Bernard head hallmark. Gold plate wears through at lug edges, crown threads, and the caseback rim. A base metal core shows a different colour at those points.
Check 2: movement and papers
Calibre 8910 is hand wound. There is no rotor. A Trésor with an automatic rotor, a date window at 3 o'clock, or a printed "Swiss Made" with uneven spacing is not from Omega. Genuine bridges carry arabesque Côtes de Genève stripes, blued screws, and a free-sprung balance with a silicon hairspring.
Every Master Chronometer ships with a card that lists eight test results and the movement number. The card number must match the movement. Omega and METAS both publish what those tests cover: 10 days, eight tests, a rate tolerance of 0 to +5 seconds a day, and exposure to 15,000 gauss.
Check 3: serial, price, sourcing
Omega stamps a serial on the movement and the case. Ask the seller for a photo of both. An Omega boutique or an authorized service center can confirm the number. Retail for an 18K Trésor sits above USD 12,000. A full-set gold watch offered near USD 500 is a counterfeit, not a bargain.
Legal status in the United States
Trafficking in counterfeit goods is a federal crime under 18 U.S.C. § 2320, with a first-offense maximum of 10 years. Selling a counterfeit also brings civil liability under the Lanham Act. US Customs and Border Protection seizes counterfeit merchandise, and a personal-use claim does not clear a counterfeit trademark.
What to do before you buy
- Buy from an Omega boutique, an authorized dealer, or a seller who gives a written return right.
- Ask for the serial photo, the Master Chronometer card, and the service history.
- Pay for an independent check by a watchmaker. Cost runs about USD 100 to 300.
- Compare the weight against a known steel watch of the same size.
- Walk away if the price, the rotor, or the missing card does not fit.