There is a compelling argument that Audemars Piguet’s ultra-thin perpetual calendars deserve almost as much credit for carrying the manufacture through the Quartz Crisis as the Royal Oak. Developed at a moment when complicated mechanical watchmaking was under existential threat, the Quantième Perpétuel Automatique combined an exceptionally thin automatic movement with one of watchmaking’s most demanding complications. The ref. 25657 followed in 1982, distinguished by its recessed calendar sub-dials and beautifully restrained 36mm case. Production continued until 1993, with 1,821 examples made across all metals, of which 1,309 were yellow gold.

Dating to 1989 according to its accompanying Extract from the Archives, the example offered here is arguably the reference in its purest form: an 18K yellow gold case paired with a classical white dial and matching gold hands and hour markers. At its heart is the automatic cal. 2120/2800, based upon the legendary ultra-thin Jaeger-LeCoultre cal. 920 architecture and displaying the day, date, month and moon phase. Measuring just 36mm across and remarkably slim despite its mechanical complexity, the 25657 is a wonderful expression of the understated complicated watchmaking that defined Audemars Piguet during this fascinating period.