The Royal Oak 15400ST introduced a more modern interpretation of the classic Royal Oak profile through its expanded 41mm case architecture and stronger dial presence. Larger dimensions give the watch a bolder appearance on the wrist while preserving the defining Royal Oak visual codes including the octagonal bezel, exposed screws, and integrated stainless steel bracelet. The Grande Tapisserie dial remains central to the design, delivering layered texture beneath applied white gold hour markers.

Driving the watch is the AP Calibre 3120 automatic movement, respected for its reliability, refined finishing, and solid balance wheel construction. Through the sapphire caseback, the engraved gold rotor and decorated bridges reinforce the high horology craftsmanship behind the Royal Oak collection. The 15400ST became an important transitional reference bridging earlier Royal Oak generations with the more contemporary models that followed.