The Cubitus is Patek Philippe's squared case line, and this is the first grand complication built into it: a perpetual calendar, skeletonised, in 45mm platinum, with the movement laid out to the rectangle rather than the circle. Skeletonising a perpetual calendar is the harder version of an already hard problem — every bridge opened up is structure removed from a mechanism that must stay in beat while carrying the calendar train. What matters on examination: that the calendar steps correctly through a month end and holds its leap-year position; that the openworked bridges show no distortion; and that platinum's softness has not been dressed out of the case by polishing. Service history and set completeness are confirmed through the desk. Maker: Patek Philippe. Reference: 5840P-001. Available through ELITA's private desk — verification review, discreet handling and storage. Price on request.