Short answer
A replica Audemars Piguet perpetual calendar sold under the code 3399 is a 1:1 first-copy build of the Royal Oak Perpetual Calendar layout. It uses a four-subdial dial, a moonphase at 6 o'clock, an octagonal bezel with eight hex screws, and a self-winding movement decorated to resemble the Audemars Piguet calibre. The number 3399 is a factory batch identifier used by replica sellers. It is not an Audemars Piguet reference number, so treat it as a way to compare batches, not as proof of anything.
What the 3399 code covers
Factories label production runs with internal codes. The 3399 tag typically points to a specific dial color, case finish, and movement variant produced together. Two watches sold as 3399 from different sellers can differ in dial texture, bracelet taper, and movement finishing. Ask the seller which batch the watch ships from and request photos of the actual unit, not stock images.
Prerequisites before you inspect
- Digital calipers for case diameter and thickness
- 10x loupe for dial and caseback detail
- 1.4 mm screwdriver for bezel screws and bracelet links
- A timing app or timegrapher for rate and beat error
- A soft microfiber cloth and a clean, well-lit surface
Step-by-step inspection
- Measure the case across the bezel at 3 and 9 o'clock and write down the diameter.
- Measure case thickness from the caseback to the top of the crystal with the calipers closed on the watch.
- Weigh the watch on a kitchen scale and compare the number against the seller's stated figure.
- Look at the eight bezel screws under the loupe and confirm each slot lines up with the case edge.
- Angle the dial toward a lamp and check that the tapisserie squares are cut, not printed, and that they line up with the subdial rings.
- Set the calendar functions in the correct order, starting with the crown and then the recessed pushers, and watch for skipped clicks.
- Push the moonphase corrector once and confirm the disc advances a single step instead of jumping.
- Check each subdial hand at 12 o'clock and note any offset from the printed markers.
- Turn the watch over and read the caseback engraving with the loupe for shallow or uneven lettering.
- Wind the crown 30 turns and listen for rotor rattle when you tilt the case.
- Run the watch face up for 24 hours and record the rate and beat error from the timing app.
- Feel the bracelet edges along the underside of your wrist and check that the links flex without grinding.
Where first-copy builds fall short
- Moonphase discs often use a printed foil instead of a lacquered or stone disc.
- Subdial hands can be a fraction of a millimeter short of the genuine proportions.
- Movement decoration is applied by machine, so the anglage lacks the hand-finished bevel of the original.
- Case thickness usually runs slightly over the genuine measurement because of the movement spacer.
- Water resistance is rated by the seller, not tested, so keep the watch away from pools and showers.
Care and service basics
Keep the crown pushed in when you are not setting the calendar, because dust enters through an open crown tube. Have the gaskets checked once a year if you wear the watch daily. Store it on a winder only if you want the perpetual calendar to stay set, since resetting a four-subdial calendar by hand takes patience and the pushers are the most fragile part of the case. Note that US customs rules restrict the import of counterfeit goods, so check your local rules before you buy.