Geneva, Nov 06, 2022

LOT 476

Patek Philippe
Ref. 738, pocket chronometer, so-called “Deck-Watch”, especially made for scientific purposes, Guillaume balance, Bulletin of the Astronomical Observatory of Geneva, Honourable mention; silver

CHF 15,000 - 30,000

EUR 15,500 - 30,900 / USD 15,000 - 29,900 / HKD 118,000 - 236,000

Sold: CHF 35,000

Very fine, silver (0.925), open-face, keyless-winding, round-shaped, pocket chronometer, so-called “Deck-Watch”, especially made for scientific purposes, with subsidiary seconds at 6.

Silver colour dial, with large suspended Arabic numerals; blued steel “Spade” hands.

19’’’ movement, rhodium-plated, going barrel, straight-line lever escapement, cut bimetallic compensated Guillaume balance with gold poising screws and blued steel hairspring with terminal curve, polished steel index-regulator with swan-neck spring and micrometric screw, adjusted by the precision timer “régleur” H. Wehrli, Geneva, “Poinçon de Genève” (Geneva Quality Hallmark or Geneva seal) stamped twice.

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Grading System
Grade: AAA


Case: 3-8


Slightly scratched

Movement: 3*


Overhaul recommended, at buyer's expense

Dial: 3-8-01


Slightly scratched

HANDS Original

Brand Patek Philippe, Geneva

Model “Deck-Watch” having won a First Class Bulletin de marche from the Astronomical Observatory of Geneva (Honourable mention with 624 points)

Reference 738

Year 1921

Movement No. 191 008

Case No. 625 943 (by “FFBA”, Fédération de Fabricants de Boîtes Argent, S. Graber, Renan)

Material silver

Diameter 60 mm.

Caliber 19’’’, straight-line lever escapement, Guillaume balance, index regulator with swan-neck spring and micrometric screw

Signature dial, case and movement

Accessories Extract from the Archives, copies of the Bulletin of the Astronomical Observatory of Geneva (1932, 1933 and 1934)


The Extract from the Archives, dated November 8, 2017, mentioned that this watch was made in 1921 and sold on January 30, 1942.


At the timing contest organised in 1934 at the Astronomical Observatory of Geneva, this chronometer was awarded a First Class Bulletin, with Honourable mention.
It was ranked 38th out of 40, with 624 points on a possible total of 1 000.
The first obtained 862.5 points and the last classified 617 points.
Abstractof the timing contest
  • Mean average daily rate +/- 8.48
  • Mean average corresponding to a change of position +/- 3.42
  • Error of compensation (per 1° centigrade) +/- 0.072
  • Restart period + // - 0.4


A “deck-watch” is a precision watch used on the deck of boats for navigational purposes (point reading) to avoid disturbing the proper functioning of the marine chronometer, which remains in a specific area of the ship (chronometer room or captain’s cabin).

For more information on this type of time-keeper, now a collector’s item, see Norbert Eder’s reference book.

· Eder, Norbert, Beobachtungsuhren, Deck Watches und Chronomètres de bord, Munich, Callwey Verlag, 1987 (216 pp.; similar watch on the cover).


Guillaume Balance

The Guillaume balance is a compensated bimetallic balance, made of anibal (an alloy of steel and nickel) and brass, after the works of Dr. Charles-Edouard Guillaume (1861-1938), with which the middle-temperature error is practically eliminated.

The middle-temperature error (or Dent’s anomaly), is the difference between the rate of a chronometer at the mean temperature and the average of the rates at extreme temperatures.

This type of balance was used by the horological manufactories since 1904.


Real scarcity of real chronometers

By the end of the 19th century, the Swiss watch industry produced millions of watches. Each year, an infinitesimal part of them are especially manufactured and adjusted to be presented to the annual chronometrical contests of the observatories of Geneva or Neuchâtel.

With the improvement of production techniques, the observatory regularly reinforces the rules of the contest; this competition becomes, every year, always more difficult. On the very small quantity of watches subjected to the rigorous and impartial control of the observatories, a good part is rejected; only the best pieces remain in the running.

Winning a Bulletin de marche – especially one of “First Class” – allows watch manufacturers to prove their chronometry skills. The same applies to the distinctions obtained at industrial or artistic exhibitions, whether at regional, national or universal level. At a time when marketing and advertising do not exist, this is the only real way to promote a company to the public and potential customers.