Answer first
Jaeger-LeCoultre makes a women's watch called the Rendez-Vous Moon. It has a moon-phase window at 6 o'clock. "Back of the moon" is not an official Jaeger-LeCoultre name. It is a phrase from resale and replica listings. It can mean two things: the unlit part of the moon disc, or the second moon painted on the far side of that disc. Replica sellers use it as a label. Check the movement before you check the label.
The reference, in facts
- Collection: Rendez-Vous, a Jaeger-LeCoultre line for women.
- Moon-phase versions come in 34 mm and 36 mm cases.
- Case metal: stainless steel and pink gold. Some references carry a diamond bezel.
- Dial: mother-of-pearl or guilloche, under a sapphire crystal.
- Moon window: 6 o'clock, on a disc printed with stars.
- Movement: in-house automatic with a moon-phase module. Jaeger-LeCoultre publishes an accuracy figure per calibre.
What a moon phase does
A standard moon phase runs on a 59-tooth wheel. The disc turns once in 59 days. Two moons sit on the disc, 180 degrees apart, so each lunar month shows one moon. The true synodic month is 29.53 days. The 59-day gear is close, not exact. The display drifts one day in about 2 years and 8 months, then needs a correction at the crown.
That gives you a test. Track the disc for 24 hours. On a real moon phase the moon moves about 12 degrees, near 1/30 of a full turn. On a day and night disc it moves 360 degrees in 24 hours, so the moon leaves the window in about 12 hours. Day and night discs sit in many low-tier replicas of this model.
What "back of the moon" covers
Reading one: the unlit half of the moon disc. As the month passes, the shadow crosses the window. Reading two: the second moon on the disc, hidden under the dial until the first one rotates out. Neither reading is a model name. Jaeger-LeCoultre does not list a Back of the Moon in the Rendez-Vous catalogue.
Replica tiers
- Quartz tier. Battery movement. Moon window is a printed disc or a day and night wheel. Case sizes often run 1 mm to 2 mm off the listed figure.
- Automatic tier. Automatic movement, moon window linked to a 24-hour wheel. Case and dial sit closer to the reference.
- Moon-phase tier. Separate moon module with a 59-tooth wheel or a copy of it. Fewer sellers stock this tier. Price is higher.
Factory names change. A name used in 2021 may cover a different build today. Ask the seller for the movement name and a photo of the caseback.
Checks before payment
- Measure the case with calipers. Compare to 34 mm or 36 mm.
- Set the moon phase to full moon, wait 24 hours, compare photos.
- Confirm the corrector position. On some references the moon corrector sits on the case side.
- Ask for the movement name. "Automatic" alone is not an answer.
- Water resistance claims on replicas have no test data. Assume none.
- Diamond bezels on replicas use lab stones or glass. Ask which.
What this guide cannot tell you
We have no build sheets for replica factories. We cannot confirm that any listing matches a real reference. Movement specs, case dimensions and stone counts change without notice. Jaeger-LeCoultre publishes full specs for the genuine Rendez-Vous Moon; use those numbers as the baseline. For moon-phase accuracy, read the brand page for the exact calibre. The figure is not the same across the line.