
The minute repeater
On demand, the minute repeater strikes the
hours, the quarter-hours, and then the minutes
that have elapsed since the last quarter-hour. The
first hammer strikes the hours on the low-pitched
gong with one strike for each hour. Subsequently,
each quarter-hour is sounded as an alternating
double strike by two hammers on both the high-
and low-pitched gongs. Finally, the second ham-
mer strikes the high-pitched gong to count the
number of minutes that have passed since the last
quarter-hour.
At 12:59, for instance, the melody consists of 12
low sounds, 3 double high/low sounds, and 14
high sounds (totaling the maximum of 32 strikes).
The tourbillon
In the course of the 18th century, watchmakers
discovered that the rate deviations of their mo-
vements were, in the final analysis, caused by the
tiny hairsprings which together with the balance
constitute the oscillator of every timepiece. Since
its center of gravity does not coincide with the
geometric center of the spring, the regular brea-
thing of the hairspring is negatively affected by the
earth’s pull in any orientation except horizontal.
The tourbillon corrects this systemic “positio-
nal” error. This is done by integrating the balance
and the escapement in a hinged cage that rotates
about its axis once a minute. On this orbit, the
slightly eccentric center of gravity of the hairspring
revolves around the center of the cage every 60
seconds, so the positional error is automatically
offset by progression, regardless of the orientation
of the spring.
Instantaneous perpetual calendar with
aperture displays
At midnight 2 minutes, all calendar displays ex-
cept the moon phase and the day/night indicator
simultaneously and instantaneously advance to
the next day and, as the case may be, to the next
month and the next year.
The perpetual calendar automatically recognizes
months with fewer than 31 days and switches di-
rectly from September 30 to October 1 and from
February 28 to March 1.
In leap years, which are indicated by the Ro-
man numeral IV in the aperture between 4 and 5
o’clock, the date disk first indicates February 29
before switching to March 1 a day later.
If the watch is wound every day, the perpetual
calendar will not need to be corrected until Fe-
bruary 28, 2100. The year 2100 is a secular year in
which the leap day is skipped according to the
rules of the Gregorian calendar.
The reference 5207 is a Patek Philippe perpe-
tual calendar in which the date correction
push piece acts only on the date and does not
change the month and year displays.