The Short Answer
A fake Ladybird 2131 is a counterfeit Rolex Lady-Datejust 31 built around a copy of the Rolex 2100-family movement. The copy gives itself away in five places: crown action, date font, rehaut engraving, case weight, and movement finishing. Work through those checks in order and you can separate a genuine watch from a counterfeit before you open the case.
What Calibre 2131 Is
Calibre 2131 belongs to the Rolex 2100 family, the self-winding generation that powered mid-size and ladies' Datejust models before the current 2200 series. It runs at 28,800 vibrations per hour, uses a bidirectional perpetual rotor, and drives a quickset date at 3 o'clock. Rolex finishes the plates and bridges with Geneva stripes and circular graining, then stamps the calibre number beside the balance. Counterfeiters copy the outward look of the watch and skip that work. That is why the movement is the first place a fake shows.
Prerequisites
- A 10x jeweller's loupe
- Digital calipers
- A jeweller's scale accurate to 0.1 g
- A bright, diffuse lamp
- Published dimensions and weight for the reference you are checking
- A case back opener matched to the model, used only with the seller's permission
How to Check a Ladybird 2131 Step by Step
- Write down the reference number engraved between the lugs at 12 o'clock and match it to Rolex's published data for that reference.
- Measure the case across the bezel with the calipers and compare the reading to the factory figure for a 31 mm Lady-Datejust.
- Weigh the watch head on the scale. Solid gold and steel cases land close to the published weight, and copies run light because the metal is thinner.
- Unscrew the crown and wind the watch through 20 turns. The 2100-family movement winds with light, even resistance. A copy feels gritty or slips.
- Pull the crown to the first position and cycle the date through six numbers. The date should jump at midnight with a clean snap, not creep across the window.
- Set the watch to six o'clock and put the loupe on the dial print. Genuine letters have sharp edges and flat ink. Copies bleed at the corners.
- Compare the date numerals and the cyclops magnification to reference photographs. The window should sit square to the minute track and magnify at about 2.5x.
- Read the rehaut engraving at 6 o'clock with the loupe. Factory engraving keeps an even depth all the way around and lines up with the minute markers.
- Spin the rotor with the watch face down. A genuine rotor turns with almost no sound. A copy rattles or scrapes.
- Check the clasp code and the end link fit against the case reference, then ask a watchmaker to open the case back if the seller agrees and the price justifies the cost.
Red Flags That End the Inspection
- Date numerals with rounded corners or uneven stroke weight
- A crown that feels loose when screwed down or carries the wrong number of dots
- Rehaut engraving that fades or drifts off the minute track
- Dial text with fuzzy edges, wrong spacing, or a flat finish
- A rotor that rattles when you tilt the watch
- A case back with shallow laser etching instead of deep stamping
- Box, papers, and hangtags that do not match the reference number
Before You Pay
Ask for clear photographs of the movement, the reference engraving, and the serial. Ask about service history and whether the watch comes with a return window. A price far below the market rate for a Lady-Datejust 31 is the strongest single sign of a counterfeit, stronger than any detail on the dial. If the seller refuses an inspection by an independent watchmaker, walk away.