longines and perrelet chronographs

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LONGINES AND PERRELET CHRONOGRAPHS
That date display’s two large disks are coplanar and positioned
adjacent to one another. So that the digits on each disk
would be the same size, the disk for the “tens” column is printed
with 10 numerals (repeating the sequence 0,0,1,2,3) and
completes one full rotation every two months. It also advances
from the first zero to the second zero when the 4th changes to
the 5th, so rather than advancing only four times per month, it
moves ahead five times each month. The Longines watch displays
the date on a printed ring that completes one full rotation
every 31 days. The motion-work propels the date disk one increment
further along at the stroke of midnight each day. The
date display of each chronograph can be quickly reset via the
crown, which must first be pulled to its middle position and
then turned until the digits in the date display correspond to the
current date.
The ETA/Valjoux 7750 is an exemplary device: it’s produced
in large numbers and it’s extremely precise in its mode of construction,
reliability and fine adjustment. The rocking pinion for
the chronograph mechanism is a movably mounted arbor with
two sprockets: the one on the dial side meshes with the fourth
wheel of the movement; pressure on the start button causes the
sprocket on the opposite side to pivot and mesh with the
chronograph’s center wheel. This puts the chronograph into the
156 WatchTime December 2008
The Perrelet’s big date
is displayed on a pair
of equally sized disks
positioned in the same
plane. The middle bar
conceals the slight gap
between the disks.
SPECS
PERRELET BIG DATE CHRONOGRAPH
Manufacturer: Perrelet SA, Bienne,
Switzerland
Reference number: A1008/3
Functions: Hours, minutes, seconds, big
date, chronograph
Movement: Perrelet P-091, based on ETA
2892, automatic, with Dubois Dépraz
4500 chronograph module, 28,800 vph,
49 jewels, Incabloc shock absorption,
Nivarox hairspring, Glucydur balance,
eccentric-weights fine adjustment, approx.
46-hour power reserve, diameter =
30 mm, height = 7.3 mm, decorated with
circular graining, skeletonized rotor,
blued screws
Case: Stainless steel, non-reflective
sapphire crystal in front and back, waterresistant
to 5 ATM
Strap and clasp: Crocodile leather strap
with double-folding clasp
Dimensions: Diameter = 41.9 mm, height
= 14 mm, weight = 102 g
Price: $4,650