Short answer
Back of the moon is listing language, not a Jaeger-LeCoultre reference name. On a Rendez-Vous copy it points to one of two things: a moon disc set behind the dial so the moon face turns away from the wearer, or a moon image on the caseback. The genuine line is the Jaeger-LeCoultre Rendez-Vous Moon, a women's watch with a moon aperture at 6 o'clock. No official JLC reference carries the words back of the moon.
What the genuine watch is
Jaeger-LeCoultre launched the Rendez-Vous collection in 2012. Moon phase versions show a moon aperture at 6 o'clock, centered under the 12. A standard moon phase tracks the synodic month: 29 days, 12 hours, 44 minutes. The common 59-tooth disc runs that cycle in two turns and drifts one day in about two years and seven months.
Dial checks
- Moon aperture position. On the genuine watch it sits at 6 o'clock.
- Moon face. Genuine discs show a face in profile. Copies print a full circle or a flat disc with no shading.
- Star field. The blue or night-sky background should be uniform. Look for visible dots at 10x magnification.
- Date window. Check alignment and font weight against the reference number.
- Hands. Rendez-Vous hands are thin and long. Short or thick hands are a tell.
Caseback and rotor
If the listing phrase points to the back, the caseback is the part to inspect. Gold Rendez-Vous references use a display back with an engraved rotor. Copies use brass rotors with plating. Plating wears at the rotor edge and leaves a yellow ring on the movement plate. Caseback engravings on copies come from a laser. Genuine engraving has depth and a matte floor.
The one test that matters
A moon phase must move. Set the moon to full, note the date, and advance the hands 24 hours at a time with the crown. The disc should step one position per day. Many copies drive the moon disc from the hour hand through a friction fit, so the disc slips or jumps several positions. If the disc moves less than one step in 24 hours, the complication is decorative.
Size and fit
Rendez-Vous cases run from about 30 mm to 39 mm across the line. A 36 mm case on a 6.5 inch wrist sits flush. Check lug width before you buy a strap. Copies often list 18 mm lugs on a case that takes 17 mm.
Movement and water resistance
Genuine moon phase Rendez-Vous watches use a mechanical automatic caliber with 40 hours of power reserve or more. Replica versions use a modified automatic or a quartz module. Water resistance on a dress watch of this type is 3 bar, or 30 m. That covers splashes. It does not cover swimming. Copies that claim 100 m without a screw-down crown are overstating the case.
Price bands
Replica Rendez-Vous Moon listings fall in three bands: about $120 to $250 for quartz or non-moving moon discs, $250 to $450 for automatic movements with a working moon phase, and $450 to $700 for better finishing, sapphire crystal, and closer dial printing. Price tracks the movement and the dial, not the case shape.
Not known
Factory names change and are not published. Two sellers can list the same photos under different names. There is no public database that ties a replica Rendez-Vous caseback number to a maker. Treat any claim of a specific factory as unverified.