For SIHH 2018, Audemars Piguet has created the world’s thinnest self-winding perpetual calendar. Here’s how it was done
By Chris Hall

When we write about ultra-thin watchmaking, we tend to focus on the outright record-setters. The watches – predominantly from Piaget, Bulgari and Jaeger-LeCoultre – which stake a claim to new ground, albeit often by tiny margins, in the simplest expression of mechanical watchmaking: thinnest mechanical watch, or thinnest automatic watch.
There?s something fitting about that; the quest for ever slimmer movements and watches is bound up with simplicity, with the reduction of things to their most essential, so it feels right to be talking about watches concerned only with hours, minutes and maybe seconds. Similarly, when we talk about Audemars Piguet concept watches, we have an image that comes readily to mind. The ?stormtrooper? type of Royal Oak Offshore models, or the RD#1 Minute Repeater, dubbed the Supersonnerie.
The Audemars Piguet Concept RD#1 Supersonnerie
Approaching Audemars Piguet?s second advanced concept watch is a bit confounding, then: here?s the silhouette of something we know intimately – the Royal Oak – with a familiar perpetual calendar dial that?s devoid of unusual registers or asymmetrical apertures. Concept" What concept"

It?s true that there hasn?t been much attention on slimmed-down highly complicated watches lately. That there haven?t been many is partly for the very obvi...