CH 28-520 IRM QA 24H

About the Patek Philippe CH 28-520 IRM QA 24H

It has a column wheel and a vertical clutch, so the chronograph seconds hand can run continuously as a seconds hand, and the elapsed hours and minutes share one subdial at 6 o'clock. The annual calendar shows the day, date and month in windows, the power reserve at 12 and a day-night indicator beside the 24-hour scale. It has 40 jewels, a 55-hour reserve and a beat of 28,800 vph at 33 mm across, and carries the Patek Philippe Seal. The chronograph piece explains the architecture.

In the library it powers 17 Complications references, the 5960 in platinum, rose gold and, from 2014, steel, and the 5961 with a baguette bezel. 7 are limited editions.

The CH 28-520 is the same chronograph without the calendar in the 5905 and the Nautilus 5980, and the glossary defines the annual calendar.