BY MICHAEL THOMPSON
Backstory
REAR VIEWS OF NOTE
Greubel Forsey
QP À ÉQUATION
NOT LONG AGO, GREUBEL FORSEY
DEBUTED A 5N GOLD version of its QP à
Équation, an exquisite ultra-complicated
timepiece with complete perpetual calendar,
tourbillon and equation of time function.
The watch, which was awarded the Grand
Prix d’Horlogerie de Genève award for the
best Calendar in 2017, utilizes a type of
‘mechanical computer’ to manage all the
changes in the displays.
This ‘computer,’ which is Greubel Forsey’s
seventh ‘invention,’ is an entirely integrated
twenty-five-part component composed of a
stack of cams with movable fingers that
shift the indications on the dial and
caseback. The month’s cam changes the
month as seen on the front of the dial.
But at the same time, different cams
within that stack move the Equation of Time
disc, the year indicator and the seasons
indication disc on the back, which is the
focus of this issue’s Backstory page.
With it color-coded indicators, the
Equation of Time display is the most visible
of the back displays. Essentially, the
Equation of Time is the conversion factor
between solar and mean time. This still
rarely made complication seeks to
distinguish the difference between solar
time and mean time, which can vary from a
few seconds to as much as sixteen minutes
during the year
Greubel Forsey’s QP à Équation makes
these calculations internally. The
watchmaker-led construction team created
an easy-to-read, color-coded display of the
results on the caseback. The red portion
shows when the sun is ahead of the solar
mean time while the blue means the sun is
behind solar mean time. On the number
scale, you see how many minutes the time is
behind or ahead. The other colors show the
seasons, the months are indicated using
letters and two semi-circles show the
equinoxes. An also-rare four-digit indicator
displays the year.
And finally, if you’re wondering how all
these calculations are made, feel free to
watch the ‘mechanical computer’ itself,
which is visible directly below a sapphire
disc.
114 | INTERNATIONAL WATCH | SPRING 2020
THE ESSENTIALS
CASE
43.5mm by 16mm 5N Gold
MOVEMENT
36.4 mm by 9.6mm, 624 parts total w/86 tourbillon cage
parts, flat black-polished steel tourbillon bridges, 75
olive-domed jewels in gold chatons, two coaxial series-
coupled fast-rotating barrels (1 turn in 3.2 hours), 21’600
vibrations/hour with a power reserve of 72 hours, Phillips
terminal curve, Geneva-style stud, nickel silver main
plates, frosted and spotted with polished beveling and
countersinks, straight-grained flanks, nickel-palladium
treatment, four engraved gold plates, one with the
individual number, synthetic sapphire mechanical
computer bridge.
PRICE
$695,000.