Short answer
Reference 131.23 is a case-back code tied to 1960s Omega Constellation watches. It is not a model name. Omega public reference material from that era lists numbers such as 14381, 168.005, 168.017 and 168.022. No 131.23 entry shows on Omega's site today. A listing that calls 131.23 a model name is seller text, not factory documentation.
What the number covers
Omega stamped case references inside the case back and on the movement ring. Numerals such as 131.23 sit in that spot. One case reference can carry several dials, hand sets and bracelets. That is why sellers pair 131.23 with terms like pie-pan or C-case.
Line specs from the period
- Case width of 34 to 35 mm on most steel and gold-capped versions
- Calibers 551, 561 and 564, each chronometer rated
- Automatic winding, 24 jewels, sweep seconds on some calibers
- Acrylic crystal
- Pie-pan dial on early pieces, flat dials on later ones
- Star emblem and the word Constellation above 6 o'clock
- Case back with the Observatory medallion in relief
Measure lug width before buying a strap. This era runs 18 mm to 19 mm.
How replicas handle 131.23
Replica Constellations sold under this code copy the 34 mm case, the star logo and the medallion. Gaps show in four spots: engraving depth, font weight, dial print and movement. Few replica factories cut a vintage case reference with correct spacing and depth. Letters look shallow. Original 1960s stampings sit deeper in the metal and hold tool marks.
Movements range from Chinese quartz to Seagull ST2130 and ETA 2824 clones. Ask for photos of the actual movement, not stock images.
Checklist before payment
- Case width in millimeters, measured with calipers
- Lug width, 18 mm or 19 mm
- Crystal type, acrylic or sapphire
- Movement name and beat rate
- Dial print under 10x magnification
- Case back medallion, struck relief or flat etch
Price and limits
Replica Constellation dress watches sell for $80 to $400. Price tracks the movement and the dial finish, not the reference number. No replica holds value, and none should pass as an Omega. A documented 1960s steel Constellation with papers sells for thousands. A low price plus a claim of vintage original is a contradiction.