The other quite exciting feature of this watch, of course, is that it can chime both home time, and local time, on demand. You can switch between the two using a push piece set into the crown, which gives the watch rather the look of a monopusher chronograph – for a reason, as we’ll see. Pushing the crown in, in addition to switching the chime, also changes the indicator on the dial that shows whether home or local time will ring. Now, the reason this repeater looks a bit like a monopusher chronograph is that, in order to coordinate the various safety mechanisms, and to switch back and forth between home and local time, Panerai uses the mechanism every watch maker thinks of first when several functions need to work both together, and in sequence: a column wheel.
How does the movement, caliber P2005/MR, manage the trick of switching between home and local time for the repeater? Well, although the problem is a challenging one, it can be simplified a bit when you remember that for a watch that shows only whole hour offsets from GMT (in other words, virtually all GMT watches) the two chiming sequences will be exactly alike except for the hours struck. This means you don’t need duplicate sets of hour, 10-minute, and minute cams; you just need two sets of hour striking mechanisms. Still, this is by no means a simple thing to build into a watch (especially one where a lot of room is already taken up by a tourbillon and two mainspring barrels, plus the repeater works). In the caliber P2005/MR, the two hour striking mechanisms are built one on top of the other: two sets of racks, which wind two sets of spring barrels, as well as two sets of hour cams. Depending on the position of the column wheel, either the upper or lower set is used – chiming either home or local hours.