This Vacheron Constantin reference 4010U is the Patrimony Moon Phase Retrograde Date in rose gold — the complicated expression of the maison's purest and most classical dress line. It pairs two poetic complications: a retrograde date, its hand sweeping an arc and springing back at month's end, and a precision moon phase so accurate it needs correcting only once every 122 years. Driving them is the in-house self-winding calibre 2460 R31L/1, finished to the standards of the Hallmark of Geneva. The 18k rose gold case measures 42.5mm in height and width with a thickness of just 9.7mm, slim and elegant for a watch carrying two complications. The silvered opaline dial keeps the Patrimony's clean, 1950s-inspired lines, with applied rose gold markers, a beaded outer minute track and two gold moons set against a starry sky.