The short answer
"Fake ladybird 2131" is a seller's tag, not a model name. "Ladybird" is slang for the Rolex Lady-Datejust, the small ladies' Datejust. "2131" is a code that listings hang on a movement version or a production batch. Rolex never built a caliber called 2131. The real numbers in that family are 2130 (no date) and 2135 (with date), which ran the 26mm Lady-Datejust, plus 2236, which powers the current 28mm Lady-Datejust and the 31mm Datejust. When you see 2131 in a title, read it as marketing, not spec.
Where the nickname comes from
Forums and group chats needed a short word for the ladies' Datejust, and Ladybird stuck. The number is looser. Some sellers use it to mean "updated movement," some use it as a batch stamp, and some copy it from a competing listing without knowing what it stands for. That is why two sites can both advertise a 2131 and ship you two different watches.
What is actually inside
Most ladies' replicas at this tier run one of three things.
- A small Asian automatic built around the ETA 2671 pattern. It is a 17.2mm movement designed for ladies' cases, and it can keep decent time and be serviced.
- A cheap low-jewel automatic with a stamped rotor. It may run out of the box, but the finishing is rough and the parts are not standardized.
- Quartz. This is a hard tell. Rolex stopped selling quartz watches when the Oysterquartz line ended in 2001, and no Lady-Datejust ever took a battery.
If a listing claims 2131 and also claims a Seagull ST2130, slow down. That movement is an ETA 2824-2 clone at roughly 25.6mm wide, sized for full-size cases. It does not drop into a 26mm ladies' case without a spacer or a different case design.
How I check one before paying
- Case size. Measure it yourself. 26mm, 28mm, and 31mm are the sizes that matter, and the dial and bracelet should match the number.
- Crystal and date. The cyclops should magnify the date about 2.5x. On cheap fakes the date looks flat, or the lens sits crooked.
- Dial print. Under a loupe the coronet and the text should have clean edges. Thick or fuzzy printing shows up a lot on this tier.
- Bracelet and clasp. End links should sit flush against the lugs. If a fingernail catches in the gap, the case is cheap.
- Crown and winding. The crown should thread smoothly and the movement should feel even as you wind it, not gritty.
- Weight. A ladies' watch is light either way, so this tells you less than it would on a Submariner. The bracelet still should not feel hollow.
Price and red flags
Ladies' replicas sit lower on the price ladder than men's sport models, which is exactly why the low end is crowded with junk. A seller who shows no movement photos, no case-back shot, and no size measurement is telling you something. So is a listing that promises "1:1 Swiss" on a watch that costs less than a dinner. Nobody is putting a Swiss movement in a $90 ladies' watch.
Legal and shipping reality in the US
Counterfeit watches are illegal to import and to sell in the United States. Customs can hold or seize a package, and the letter you get in the mail is not a refund. If you resell, you move from a buyer's risk to a trademark problem, and branded boxes and papers make that worse rather than better. Payment is usually the other trap: most sellers want methods with no chargeback path, so a seized or dead watch is money gone.
Bottom line
If you want the look of a Lady-Datejust, the honest move is to buy a small automatic from a brand that stands behind its movement. If you buy a replica anyway, ignore the 2131 in the title, ask for movement photos, confirm the case size in millimeters, and know that the number on the listing tells you nothing about what lands in the box.