The steel Patek Philippe 1518 is one of only four known examples and is expected to fetch $20 million via private sale.

blue translucent enamel centre dial, signed by both Patek Philippe ... particularly from Patek Philippe. Perpetual calendars and chronographs of the era have been fairly heavily talked about ...

For Patek Philippe, substance comes at no compromise to style in the Ref 5326G-001 Annual Calendar Travel Time ... with an intricately embellished outer rim – the textured charcoal dial is circled ...