After 5 years of research and development, this year at SIHH 2018, Audemars Piguet unveiled their latest concept watch – the world’s thinnest self-winding perpetual calendar wristwatch.

The Royal Oak RD#2 comes in a 6.3 mm thin case, almost 2 mm thinner than the Royal Oak Extra Thin, which is pretty incredible considering that it’s a perpetual calendar.

While only a concept at this point in time, the new benchmark achievement is a tribute to AP’s long history of thin, perpetual calendar, and complicated watches in general.

It took 5 years to engineer caliber 5133, which is 2.89 mm thick, because AP watchmakers had to reduce the three-level movement to a single level, which required rearranging of the functions, without sacrificing efficiency or robustness.

The 2.75Hz automatic movement has 37 jewels, 256 total components, a 40-hour power reserve and a 2.89 mm thick skeletonized center mounted rotor.

The 41 mm diameter watch case and metal bracelet are made from 950 platinum.

Giving the watch an unmistakable appearance is a blue Grand Tapisserie dial, with blue counters, white gold applied hour markers, and 12 o’clock position for the moon phase which pays homage to the first AP Perpetual Calendar wristwatch from 1955.