Double dial cylinder watch with equation of
time and calendar dials by David Pons
Paris, France, around AD
1770
This splendid example of an 'equation
of time' watch has two dials. The main dial, on the front,
shows the hours and minutes in the normal way. It also has a
polychrome enamel border decorated with the signs of the zodiac and
a scale with the months and the number of days in each. There are
two minute hands on the watch. The gold hands on the main dial show
true solar hours and minutes, with the uppermost hand showing mean
solar minutes. The steel hand turns once per year to show the date.
In the middle, the inscription 'Solis ad instar'
indicates that the dial shows the time according to the
sun.
The white enamel dial
on the back shows the days of the month and mean solar hours and
minutes. Both dials, signed 'Coteau' on the
reverse, were made by Joseph Coteau, one of the most accomplished
dial enamellers of eighteenth century Paris. The movement is signed
'David Pons' and the fact that the regulation dial
for altering the rate of the watch is inscribed
'Avanza' and 'Ritarda' suggests
that the watch was made for an Italian
customer.
The movement,
with
fusee
and cylinder
escapement with a plain brass three-arm
balance, is housed in a gold case, glazed back and front to reveal
the dials. Inside, the case is punched with marks used in Paris
between 1768 and 1774 and also has the makers mark
'JAA', probably that of Jean Antoine Alazard of
Paris.