Short answer
"131.20" is a reference prefix, not a single watch. Omega builds several Constellation models whose numbers begin with 131.20. The prefix points to a stainless steel case with gold accents. The remaining digits set size, dial, bezel, and movement. A seller who lists "replica Constellation 131.20" with no further digits is describing a family, not a specific watch.
Omega does not publish a public decoder for its reference numbers. Read the caseback of the watch you want, then match the full 14-digit number against a reference index.
What the gen 131.20 covers
Listings under 131.20 include 25 mm and 28 mm quartz models and 29 mm automatic models. Dealers read the second block of digits as a material code. Steel and gold is the common combination in 131.20 listings. Confirm material from the caseback, since Omega changes codes between collections.
Shared traits across the group:
- Claws at 3 and 9 o'clock, polished, with a flat face.
- Mono-rang bracelet with horizontal bars and brushed center links.
- Diamond-set bezel on some references, plain bezel on others.
- Mother-of-pearl dial on many small sizes.
- Quartz caliber 4061 on the smallest sizes; Master Chronometer automatic calibers on larger ones. Check the exact reference for the caliber.
Checking a replica
- Measure the case with calipers. Common diameters are 25 mm, 28 mm, and 29 mm. Photos hide size errors. Numbers do not.
- Weigh it. A steel and gold gen weighs more than a plated replica of the same diameter. Gold plating wears at the crown and clasp first.
- Inspect the claws. Real claws sit flush with the bezel edge. Replicas show gaps and rough edges.
- Ask about the stones. Replica bezels use cubic zirconia or glass. Get the stone type in writing.
- Check the movement. Most small 131.20 replicas run quartz. A second hand that sweeps on a quartz case is a mismatch.
- Read the caseback engraving. Font weight and depth differ from gen. Reference digits on replicas sit off-center.
Price and legal notes
Omega lists steel and gold Constellation models from about 5,000 to 12,000 USD, based on size, stones, and movement. Replica sellers ask 100 to 400 USD for quartz versions. Check current retail prices before you compare.
In the US, selling or importing a counterfeit watch is illegal. U.S. Customs and Border Protection can seize shipments. 19 U.S.C. 1526 covers imported goods that carry a counterfeit mark. Buying from an overseas seller carries seizure risk and no recourse.
What to ask a seller
- The full 14-digit reference number, not just 131.20.
- Measured case diameter and weight in grams.
- Movement type and caliber number.
- Stone type on the bezel.
- Plating thickness in microns, if the seller states one.
- Photos of the actual unit, with a timestamp.
If a seller cannot give the full reference or unit photos, the listing uses stock images. Treat it as a stock listing and move on.