5402ST, Royal Oak, C-Series, Steel

The 5402 is the reference which has most defined Audemars Piguet in the modern era. Despite an initial lukewarm reception, this integrated bracelet sports watch has garnered increasing respect with every decade since. This was the start of integrated bracelets and considering the case-bracelet pair as a design—the start of Genta's rather successful pen in that category. Finally, it began the modern era for Audemars Piguet, and went on to revive what was a then-struggling brand. This is exemplary C-Series example, from earlier in series with 'AP Down', and beautifully honest.  

At debut in 1972, the 5402 was the most expensive steel watch ever made and by some margin. At 3750 CHF, it was more than four times the nearest most expensive steel watch from any other marque. Genta and Audemars Piguet were the first to treat steel as a luxury material: design first, metal second. AP executed on Genta’s design thoroughly, with an exceptionally intricate monocoque case construction. Here, the case middle and caseback are fused, with a front-loading calibre 2121 and eight bolts running through the case to meet screws on back (notably, those hexagonal bolts were only given symmetrically placed screw heads as decoration). It was then entirely hand finished with a beautiful contrast between delicate polished edges and brushed surfaces. The design is industrial, almost brutalist, but it wears with a comparable total elegance thanks to an ultra-thin profile.

At 39mm it was considerably larger than most offerings in its time, yet just 7mm thin. This made the 5402 immediately svelte on wrist and is responsible for most of its refined presence. This was thanks to an ultra-thin calibre 2121, a 19800-vph JLC 920 ébauche with gyromax balance and a beryllium rotor rail for less friction and wear. It is considered by many one of the most refined movement architectures ever. In the words of historian Michael Friedman, the 920 'stands apart as one of the most reliable, beautiful and technically innovative movements of all time.' Moreover, for the 5402, AP were able to make the calibre 3.05mm thin as opposed to the standard ébauche's 3.4mm by removing central seconds. AP's end client received a watch true to Genta's design with one of the thinnest midcase profiles ever offered.

A great degree of effort went in to creating a dial with a level refinement that could match the case and calibre. A few years earlier, Stern Frères had just inherited some old guilloché machines, and made suggestion to Genta that he use them in his efforts. Genta obliged, and Stern went above and beyond creating this pyramid-structured 'petite tapisserie'. It is a particular style of multiple hand guilloché techniques, forming square pyramids with a diamond texture on top. As they were all turned by hand, there is immense variation in the size and number of pyramids between 5402 examples, but counts are always in the high hundreds. Finally, it would be given a galvanic bath, originally a deep grey-blue. It was also the first use of the AP monogram at 6, applied in white gold. This example is a C-Series with the correct Swiss only signature as it should be. 

The Royal Oak has evolved to include many varied cases and complications. In our opinion, the original design has yet to be bettered. It was a pioneering design, let alone retail strategy and engineering. The Royal Oak's importance to watchmaking and particularly AP as a brand today can probably not be overstated. The 5402 is easily one of the most significant watches of the last century.

This 5402ST presents in excellent overall condition. Its dial shows light signs of age with a small patina visible on the base. All lume applications or original tritium, matched under UV. Its case is fantastically sharp, with strong bevels and light signs of sparing, careful wear. Bezel bolts stand flush or slightly sunken with the topmost surface. Its calibre 2121 is running well in specification on our timing equipment. The watch comes with full links, fitting up to a 7.7-inch wrist.

This example is modelled on an average-sized 7-inch wrist.