The Audemars Piguet Royal Oak Selfwinding reference 15551ST.ZZ.1356ST.02 is a 37mm celebratory timepiece released to commemorate the 50th anniversary of the iconic Royal Oak collection. This model is constructed from stainless steel and features a bezel set with 40 brilliant-cut diamonds totaling approximately 0.92 carats. The “Bleu nuit nuage 50” dial is adorned with the signature “Grande Tapisserie” pattern, accompanied by white gold applied hour-markers and luminescent Royal Oak hands. A key distinction for this anniversary edition is the dedicated “50-years” oscillating weight on the self-winding movement, which is visible through the sapphire crystal caseback.
Technically, the watch is powered by the Calibre 5900, a high-performance automatic movement that offers a 60-hour power reserve and operates at a frequency of 4 Hz. Its complications include hours, minutes, center seconds, and a date display located at the 3 o’clock position. The case maintains a relatively slim profile with a thickness of 9.1mm and is water-resistant to 50 meters. The integrated stainless steel bracelet is secured with an AP folding clasp, completing the unified design language established by the original 1972 model.
General reviews of the 15551ST frequently praise its balanced 37mm proportions, which serve as a versatile “mid-size” option suitable for a wide range of wrist sizes. Collectors often highlight the aesthetic appeal of the diamond-set bezel paired with the historic blue dial, noting that the gems add a layer of luxury without compromising the watch’s sporty silhouette. While the Calibre 5900 is noted for its efficiency and thinness, some enthusiasts specifically target this reference for the exclusive anniversary rotor, which was produced for a limited duration. Market sentiment suggests it is a highly sought-after investment piece due to its milestone status and limited production window.