Some watches tell you the time. Others tell you almost everything else as well. This charming Audemars Piguet Quantième Perpétuel ref. 25657BA falls in the second category, combining a beautifully slim 18k yellow-gold case with one of the most impressive complications in watchmaking.

A perpetual calendar is one of those complications that looks spectacular on the wrist. The watch displays the day, date, month and moon phase, but underneath the dial the movement keeps track of the different lengths of the months and even leap years. Once correctly set, the calendar can theoretically run for decades without needing a correction. Considering all of this happens mechanically, it remains incredibly impressive.

The ref. 25657BA is particularly interesting because it carries on the tradition of Audemars Piguet's ultra-thin perpetual calendar line, introduced in the late 1970s. This specific reference is produced between 1982 and 1993, yet only 1.309 examples were manufactured. Instead of the very first ref. 5548 of this charming line, the 25657 features sunken subdials where the indicators are slightly lower than the rest of the dial. A gorgeous detail, giving way more depth to the dial compared to its predecessor. At 12 o'clock sits the month indication, the day is shown at 9 o'clock and the date at 3 o'clock. The moon phase at 6 o'clock completes the calendar and adds a charming touch to this highly complicated watch. Because of this dial layout, the face is very clean and aesthetically pleasing to look at.

And then there is the dial itself. This example is fitted with a stunning Mother of Pearl dial, a material that can completely change character depending on the light. The natural surface creates subtle reflections and variations in colour, making the dial feel almost alive as the watch moves around the wrist. No two pieces of Mother of Pearl are ever exactly alike, which makes this particular execution all the more appealing. Combined with the warm 18k yellow gold, the result is a rather elegant and unusual combination. The dial itself is more contemporary, and adds just so much to the classic look and feel of this eyecatcher.

The stepped case measures 36mm and is beautifully proportioned. Condition-wise, you can easily tell someone looked after this gorgeous piece. Hallmarks and the case back numbers have a perfect readability. The slim profile is especially impressive considering what is hiding inside. Audemars Piguet managed to fit an automatic perpetual calendar into a movement measuring just 3.95mm in height. This example is powered by Audemars Piguet’s caliber 2120/2800 automatic movement, which is based on Jaeger LeCoultre’s infamous ultra-thin caliber 920 movement. This base caliber was of course used, among others, in the Audemars Piguet Royal Oak, Patek Philippe Nautilus, and Vacheron Constantin 222.

For us, that is exactly what makes the 25657BA so appealing. It dates back to ca. 1990. It combines the elegance of a classic 36mm Audemars Piguet with an incredibly sophisticated mechanical complication, topped off with the natural beauty of a Mother of Pearl dial. A rather serious piece of watchmaking, hiding behind a very charming face. The 18k yellow-gold case is complemented by a beautiful suede strap and matching AP buckle.