What "240" means in a Rendez-Vous Moonphase listing
On most replica listings, 240 is an internal stock code for a case and dial combo, not a caliber name. It gets attached to the 36mm Rendez-Vous Moon case with the moon disc at 6 o'clock, in steel or rose-gold plate, with either a silver guilloche dial or a blue sunray one. Two sellers can use the same number for watches that differ in movement, crystal and dial print. So before you compare prices, ask which reference the seller mapped it to and what movement sits inside. That answer tells you more than the number does.
How the moonphase is supposed to work
A real moonphase is a 59-tooth disc geared to the hour train. It advances one tooth per day and finishes a full cycle in 29.53 days, the synodic month. On the genuine Rendez-Vous Moon the moon and stars sit under an aperture at 6 o'clock and the disc creeps forward. Watch that disc for a minute. If it sweeps in one continuous motion or flips from moon to sun in 24 hours, you are looking at a day/night disc dressed up as a moonphase. That is the most common shortcut in this tier.
What I check before buying
- Disc, not print. The moon should be a physical disc with stars painted or stamped on it, visible as it turns under the aperture.
- Corrector or crown. Ask where the moonphase is set from. A recessed pusher near 8 or 10 o'clock, or a crown position, both exist. If the seller cannot say, they have not handled the watch.
- Dial print under magnification. The JLC wordmark and the Rendez-Vous script should hold up at 10x. Soft edges on a tiny script are the giveaway at arm's length.
- Case thickness. The reference case is slim. Moonphase modules add height, so compare the stated thickness against the real one and expect 1 to 2mm extra.
- Hands. Leaf or baton shape, blued or polished, no burrs. Look at the tip of the seconds hand in a macro shot.
- Caseback engraving. Depth and font matter. Laser etching looks flat and grey. Engraving has shadow.
Setting the moonphase without wrecking it
Do not touch the moonphase between about 9pm and 3am, when the gears are meshed and the change is in progress. Set the time to midday first, then press the corrector once per day until the disc shows a full moon, then count forward to today. If the watch has a date, set the date first, then the moon. A phone app or an almanac gives you the current phase. On a 29.5-day cycle you will drift a day every two and a half years, which is normal for this design.
Movements you will meet
Three tiers show up. Quartz with a spinning moon disc, automatic with a stock Miyota or Seiko-based movement and a bolt-on moon module, and automatic with a modified clone that keeps the case thinner. Quartz is cheapest and the moon tends to run a 24-hour cycle. The middle tier keeps decent time and the moon phase is real, but the case gets chunky. The top tier is where dial print and disc finish come close to the reference. Pay for the dial and the moon, not for a name on the rotor.
Price bands and what they buy
Under $120 buys quartz and a printed disc. From about $150 to $350 you get a true 29.5-day moonphase and a better dial. Above that you are paying for case finishing, sapphire with a box profile, and a movement a watchmaker can service. Ask for a video of the moonphase advancing under a loupe before you pay. A seller with the watch in hand can shoot it in two minutes.