Quick answer
Fake Omega 3520 listings point to the Omega Speedmaster Day-Date reference 3520.50.00. The 3520 group covers a steel automatic chronograph with day, date, month, and a 24-hour subdial. Replica sellers shorten the number to 3520 because it fits a listing title. The suffix, 50.00, identifies the dial and bracelet variant. A listing that shows only 3520 does not tell you which variant the watch copies.
What the number 3520 covers
Omega reference numbers use five digits plus a two-digit variant suffix. The first group names the case and movement family. The suffix names dial color, hands, and bracelet. The Speedmaster Day-Date case was sold with black, silver, and blue dials under different suffixes. Ask the seller for the full number stamped on the caseback. If the seller cannot name it, the listing is a stock photo set, not a described watch.
Genuine specs to compare
- Steel case, about 39 mm across and about 14 mm thick.
- Automatic chronograph, Omega calibre 1151, based on the Valjoux 7751.
- Subdials at 12, 6, and 9. Calendar windows for day, date, and month. A 24-hour hand.
- Sapphire crystal and a screw-in caseback with reference and serial engraved.
Confirm the numbers against Omega data or a printed Omega catalog for the year of production. Sales listings copy each other, and wrong specs spread from listing to listing.
Movement tells
The Valjoux 7751 base gives a fixed layout: running seconds at 9, 30-minute counter at 12, 12-hour counter at 6, plus day, date, month, and 24-hour functions. Many low cost replicas use a simpler 7750 layout and fake the calendar with printed disks or a blank window. Test the crown positions. In position one the date should click over on its own. In position two the day and month change by hand. If the month window never moves, the watch does not have the real function set.
Dial, case, and paperwork
Check print weight on the logo and the tachymeter scale, the finish on the applied indexes, and the alignment of the date window with the dial ring. On the caseback, the engravings should cut into the metal with sharp edges. Serial numbers on the Day-Date sit on the caseback rim or the lug. Papers that show another serial, or no serial, are worth nothing. A genuine 3520.50.00 trades in the low thousands of US dollars with box and papers. First copy listings sit in the tens to low hundreds of dollars. A new old stock full set at a few hundred dollars is not a genuine watch.
Checklist
- Get the full reference, not just 3520.
- Match the displayed specs to Omega data for that reference.
- Test day, date, month, and the 24-hour hand in all crown positions.
- Compare caseback engravings and serial against the papers.
- Compare the asking price to the secondary market for that reference.
Unknown points
Omega does not list a calibre numbered 3520. Some sellers use 3520 as an internal stock code with no link to the Omega reference. Photos in those listings often show a different watch than the one shipped. Treat any listing without a full reference number and a movement photo as unverified.