26586IP Audemars Piguet Royal Oak Perpetual Calendar RD2

This is not a normal Royal Oak QP. It’s the RD2, very possibly the last watchmaking-first complicated Royal Oak from Audemars Piguet which placed emphasis on their technical ability rather than their marketing ability. It looks like a Royal Oak that’s picked up intermittent fasting as a hobby, still 41mm in footprint but an unbelievable 6.3mm thin. For context, the standard ref. 15500 is 10.5mm and a normal QP is 9.6mm. But that’s far from the whole story. This is a Royal Oak that pushes technical edges in a few dimensions, a reminder of what the brand can do when they cut all the celeb-fawning, faux-handmade Bennahmias marketing to just focus on what’s possible with the Royal Oak today. Quite a lot, as it turns out.

RD here stands for Research & Development, a bit like Patek’s Advanced Research department. It’s a Skunkworks inside AP that bridges the gap between concept watches and production, offering tiny runs to AP’s most important clients with true watchmaking innovation as their core competency. This, RD2 (there have been 4 RD models) is still today the world’s thinnest QP. This was accomplished through a fundamental rework of the entire calendar architecture. Where even the very thin 5548 used three planes of bridges, a modular construction, the RD presses all that functionality into one plane of existence. What were once stacked gears and separate mechanisms were re-engineered to sit on one plane and often distilled into just singular components. The QP here is a single, flat plane of brilliance. That’s never been done before.

There’s more that’s new too. In traditional watchmaking, the dial sits atop the base plate, which the calibre is built on. In the quest for thinness, the dial here became a functional and structural part of the movement, effectively functioning as a part of the base plate. That’s never been done. It’s a bit like the greatest step forwards in F1 cars in the 70s, where the engine block first became a stressed member of a monocoque chassis, rather than being supported by the chassis around it. RD2 had a few batches. First 2018’s 26586PT (all platinum prototype, tapisserie dial, unknown production), then in 2019 this 26586IP (titanium and platinum, matte brushed dial, made in 200 examples), then finally in 2023 a 26586TI (all titanium, gradient blue dial, 200 examples again). This watch will likely serve as the basis for the next generation Royal Oak QP and its innovations will influence the next century of QP watchmaking. But the (definitely fewer than) 450 original RD2s will always have the weight of history on their side. It is the last watch I’ve seen from AP that reminds me what I love in Le Brassus. It shows just how far AP can push by asking their watchmakers ‘what have you got?’ with a blank cheque, rather than using that checque to ask Cactus Jack ‘what can we do for you?’

This example is great: light wear, nothing more, from its original owner. It comes from a well-regarded Florida retailer.