Short answer
131.13 is not a documented Omega Constellation reference number. Omega's published reference format uses six digits plus a case-material suffix, such as 168.005 or 168.017. Some replica listings use 131.13 as an internal catalog code. A few vintage sellers attach it to a steel or gold-capped case. Treat the number as a seller code, not a factory identifier.
Two Constellation families sit behind most listings with this code. The first is the 1950s and 1960s pie-pan dial model. The second is the 1980s integrated-bracelet Manhattan model. Case sizes, dials and movements differ between them. Confirm which one you are buying before you pay.
What a 131.13 listing shows
- Case diameter 33 mm to 35 mm on vintage-style builds, 36 mm to 38 mm on modern-style builds.
- Gold-capped or two-tone case with a fluted or smooth bezel.
- Pie-pan dial with applied baton markers, or a flat dial with printed markers.
- Date window at 3 o'clock on most examples.
- Automatic movement, or quartz on cheap builds.
Movement check
Genuine vintage Constellations from this era used calibers 551, 561, 564, 1011 and 1021. A replica will not use those. Common replica movements are the Miyota 9015, the Seagull ST2130, an ETA 2824 clone, and generic quartz. Ask for the movement name and a photo of the rotor. A Miyota 9015 runs at 28,800 vibrations per hour and hacks. A quartz replica ticks once per second.
No known replica of this reference uses an Omega in-house caliber. Sellers who claim a Co-Axial movement at a low price are misdescribing the watch.
Case, dial and bracelet
Check four points.
- Lug width. Vintage Constellation cases use 18 mm or 19 mm lugs. Modern builds use 20 mm.
- Dial printing. The word Constellation sits above the star on genuine dials. On many replicas the star is too large or sits too low.
- Caseback. Vintage models carry a gold Observatory medallion. Many replicas use a stamped steel plate with shallow relief.
- Bracelet. Integrated Manhattan bracelets have half-links and a signed clasp. Replica clasps show uneven engraving and loose spring bars.
Price bands
- Under $80: quartz, plated case, mineral glass, hollow end links.
- $120 to $250: Miyota or Seagull automatic, 316L steel, sapphire on some builds.
- $300 to $600: better case finishing, gold plating at 3 to 5 microns, closer dial print.
Prices above $600 for a replica of this reference are hard to justify. Genuine vintage Constellations from the 1960s sell in the $900 to $2,500 range. That changes the value math.
Red flags
- A serial number or reference that matches no published record.
- Photos copied from another listing. A reverse image search takes two minutes.
- Claims of solid gold. Gold replicas at these prices do not exist.
- No movement photo, no caseback photo, no timestamp.
How to verify before buying
Ask for the case diameter, lug width, movement name, and weight in grams. A 35 mm steel watch with a bracelet weighs 90 g to 120 g. Then compare the photos to archive images of the 168.005 and the 1980s Manhattan. If the seller cannot name the movement, skip the listing.