The History of Audemars Piguet's Moon Phase Watches, Including Key Models

Audemars Piguet, known for its numerous complicated watches, has incorporated moon phase displays into its flagship collection, the Royal Oak. We will introduce the main models and how to operate the moon phase display.

Audemars Piguet and the Moon Phase

Audemars Piguet was founded in 1875 in the Vallée de Joux, a region of Switzerland known for its highly developed watch industry and for its development of complex timepieces. Since then, the company has continued to produce timepieces with complex mechanisms featuring outstanding functions such as minute repeaters and perpetual calendars.

First, let's trace the history of the caliber 9/10RSQ, Audemars Piguet's first movement to incorporate a moon phase.

Caliber 9/10RSQ: The foundation of the calendar wristwatch

The moon phase function displays the phases of the moon using a rotating enamel moon disc combined with a small seconds hand, and the first Audemars Piguet movement to feature this mechanism was the Caliber 9/10RS.

This movement is an important part of Audemars Piguet's history, as it embodies the advanced technology of the time of its manufacture.

Of the 2811 watches ultimately produced, only 68 were 9/10RSQs equipped with a calendar function. This significant mechanism serves as the foundation for calendar wristwatches still in production today.

Moon phase design at 6 o'clock

Produced over a five-year period starting in 1945, 68 extremely rare calendar calibres were fitted to four references (reference numbers 5504, 5513, 5514, and 5515) made in various designs.

It was sold from 1949 to 67 in a variety of designs, including the 5504 with a round case measuring 37mm in diameter, which was large for the time, and the 5514 with an innovative square case.

All 68 Caliber 9/10RSQ models equipped with a calendar function were designed with a moon phase display at the 6 o'clock position.

Moon Phase Models

Audemars Piguet offers several rare models with moon phases. We will introduce three representative models. Each model is produced in limited numbers, making them difficult to obtain.

Royal Oak Day-Date Moon Phase

The Royal Oak, known as Audemars Piguet's masterpiece collection, includes a variety of models, both old and new. The Day-Date Moon Phase is a model with a date at 3 o'clock, a day of the week subdial at 9 o'clock, and a moon phase at 6 o'clock.

Although the case diameter is approximately 36mm, slightly smaller than the current Royal Oak, the displays are arranged in a balanced manner at 3, 6, and 9 o'clock, maintaining excellent visibility.

Details that characterize the Royal Oak, such as the tapestry design on the dial, the octagonal case, and the eight screws embedded in the corners, are still present.

Royal オーク パーペチュアル calendar

The Royal Oak is equipped with a perpetual calendar, considered one of the most precise structures among all complications. The perpetual calendar accurately reflects the end of each month and leap years, and will not require manual adjustment for 100 years.

In addition to the full calendar function that displays the month, date, day of the week, and moon phase, the week number is also indicated by a hand around the edge of the dial.

The moon on the moon phase display has realistic shadows created by laser processing, further enhancing the beautiful night sky at 6 o'clock.

Jules Audemars Perpetual Calendar

Along with the Royal Oak, which is developed as a luxury sports watch, the classic-looking Jules Audemars is also a famous series that continues to support Audemars Piguet.

The elegant sunray-finished dial features four subdials for excellent visibility. The delicate yet three-dimensional hands and indexes are also excellent. It is precisely because of its simplicity that the skillful finishing stands out, making this a complex watch that embodies the pinnacle of Audemars Piguet's technical expertise.

How to operate the moon phase

The moon phase operates in sync with the progression of time, but adjustments may be necessary due to slight discrepancies in the lunar cycle or the watch itself stopping.

Let's understand how the moon phase works and how to adjust it.

How the moon phase works

The rotating moon phase disc depicts two moons, and by looking at the shape of the moon displayed as the disc rotates, you can see the current phase of the moon.

The edge of the disc is decorated with 59 teeth, and the disc rotates once every 59 days. By doubling the lunar cycle of approximately 29.5 days and depicting two moons, it is possible to display the phases of the moon, which is difficult to express.

This means that during a full moon, one moon reaches the top of the disk, and during a new moon, both moons are hidden, making for a brilliant system.

Example of a Royal Oak Perpetual Calendar

The Royal Oak Perpetual Calendar only needs to be corrected once every 100 years if the watch is kept running, but if it is not worn for an extended period and there is a deviation of more than four days, it will need to be manually adjusted.

The calendar is adjusted using the pusher at 10 o'clock, the moon phase at 7:30, the leap year and month at 2 o'clock, the day at 8:30, and the week at 4 o'clock. Always use the included adjustment tool.

Then, adjust the time. If the current time is earlier than the time indicated on the clock, adjust the hands counterclockwise; if the current time is earlier than the time indicated on the clock, adjust the hands clockwise.

Incidentally, and not just for this model, calendar adjustments should not be made between 14 p.m. and 3 a.m., as this could damage the mechanism.

Have fun with the moon phase

Audemars Piguet's moon phase displays the phases of the moon at the 6 o'clock position on the dial. It is a complication that requires a high level of skill to manufacture, and the brand's signature Royal Oak and Jules Audemars models also feature a moon phase.

Experience the true joy of a luxury mechanical watch with this intricate, complex mechanism that combines design and practicality.