Short answer: most fake Breguet Classique perpetual calendar moon phase watches do not run a perpetual calendar. They run a calendar-shaped dial. The day, month and leap-year windows are driven by a small 4-year cam that looks convincing in photos, and the moon phase is often a painted disc geared off the hour wheel. Only the top tier of replicas uses a module that genuinely skips 31-day months and handles February 29.
What the genuine reference does
Breguet's Classique perpetual calendar models, the 5327 and 5447 families being the ones copied most often, display day, date, month, leap year and a moon phase on a guilloché dial, framed by a hand-fluted case band and Breguet hands in blued steel. The movement is an in-house perpetual calendar calibre, and the whole point of it is that you set the watch once and the date stays correct through every short month and every February 29 until 2100. Some references also use soldered lugs, a detail most replicas skip entirely.
The three replica tiers
- Entry tier, $150 to $350. A basic three-hand automatic with glued-on calendar discs. The leap-year window is decorative or moves on a 12-month cycle. The moon phase drifts. Date changes creep between 10 p.m. and midnight instead of snapping.
- Mid tier, $400 to $900. A real calendar module, often annual rather than perpetual. It handles 30 and 31-day months but needs a manual correction every February. Correctors are recessed and functional.
- Top tier, $1,200 and up. This is where you find a true perpetual mechanism with correct leap-year gearing. These are rare, produced in small batches, and usually the only versions worth comparing to the genuine watch on anything except looks.
The moon phase is the tell
A properly built moon phase uses a 135-tooth wheel, which holds accuracy to roughly one day in over a century. Cheaper replicas use a 59-tooth disc, which sounds close but drifts about one day every two to three years, and worse if the disc is driven by a friction fit rather than a geared train. If a seller cannot tell you the tooth count or show the moon phase advancing on its own, assume it is the simple version.
What to verify before you buy
- Ask for a video of the date change between 11:55 p.m. and 12:05 a.m. It should snap, not crawl.
- Ask for the leap-year indicator moving. It should advance once a year, not once a month.
- Confirm the setting window. Never set the calendar between 9 p.m. and 3 a.m., because the gears are mid-change and you can shear a tooth.
- Check the dial up close. On the real thing the guilloché is cut, not stamped, and the fluting on the case band is even around the full circumference.
- Look at the caseback. A real perpetual module has visible levers and springs. A printed plate with fake screws is a giveaway.
- Do not trust the water resistance rating on any replica. Gaskets are the first thing factories cut.
Price and legal reality
Expect to pay three to ten times more for a working perpetual module than for a lookalike dial, and expect long lead times. On the legal side, counterfeit watches can be seized by U.S. Customs if they are shipped into the country, and selling one as genuine is trademark counterfeiting and fraud. Buy it to wear it, keep the receipt, and disclose what it is if you ever resell.
Bottom line
If you want the look of a Breguet Classique perpetual calendar with a moon phase, a mid-tier replica delivers that at a fraction of the cost. If you want the function, meaning a calendar that actually stays set, you are shopping in a much smaller pool and you should verify the mechanism before you send money.