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The Encyclopedia of Horology

Pocket watch · Keyless pocket chronometer

L. Leroy & Cie. Keyless Pocket Chronometer

Partially verified

This 18K gold keyless pocket chronometer, manufactured circa 1913, is signed by L. Leroy & Cie., Paris. The timepiece features a three-body massive "bassine" polished gold case with a hinged cuvette. The white enamel dial displays Arabic numerals, an outer Arabic minute ring, and a recessed subsidiary seconds dial, complemented by gold spade hands. The 19-ligne movement is constructed in gilt brass and contains 20 jewels. It utilizes a brass-invar Guillaume balance adjusted by Quelos and a blued steel balance spring with a terminal curve. A key feature is the punch-mark of a viper's head, indicating it was set by the Observatory of Besançon. The watch was awarded a Bulletin de Premiere classe at the 1913 Timing Contest organized by the Observatoire National de Besançon. It is signed on the dial, case, and movement, and includes copies of the original timing records.

Front view of the 18K gold Leroy keyless chronometer with white enamel dial and subsidiary seconds.
Front view of the 18K gold Leroy keyless chronometer with white enamel dial and subsidiary seconds. — Antiquorum. Rights pending — permission not yet requested. Original source

Catalogue identity

Source
catalog.antiquorum.swiss
Category
Pocket watch · Keyless pocket chronometer
Maker / attribution
L. Leroy & Cie.
Reference
Not recorded
Catalogue / lot identifier
331
Source-reported date
circa 1913
Source-reported place
France
Source-reported serial
2769 (movement), 9288 (case)

Source-reported attribution and specifications are not independent authentication. A listing does not establish present ownership, current display, availability or permission to reproduce.

Object description

Case and Dial Construction

The pocket chronometer is housed in a three-body, massive gold case of the "bassine" style, characterized by a polished finish. The design includes a hinged gold cuvette protecting the movement.

The dial is rendered in white enamel and features black-painted Arabic numerals for the hours, paired with a distinct outer Arabic minute track. A sunk subsidiary seconds dial is positioned at the six o'clock mark. The watch is equipped with gold spade-style hands. The dial is signed by the manufacturer, L. Leroy & Cie.

Evidence for this section
  • “Three body, massive, "bassine", polished. Hinged gold cuvette.”
  • “White enamel, with Arabic numerals, outer Arabic minute ring and sunk subsidiary seconds. Gold "spade" hands.”

Movement and Chronometric Performance

The watch is driven by a 19-ligne gilt brass movement containing 20 jewels. Technical specifications include a brass-invar Guillaume balance adjusted by Quelos and a blued steel balance spring featuring a terminal curve. The movement is marked with a viper's head, identifying it as having been set and tested by the Observatory of Besançon.

The piece achieved a Bulletin de Premiere classe designation at the 1913 Timing Contest held by the Observatoire National de Besançon. Performance records indicate a mean average daily rate of +/- 0,32, a compensation error at 20° of +/- 0,136, and a mean error in two positions of +/- 3,14.

Evidence for this section
  • “M. 19"', gilt brass with punch-mark in form of a viper's head set by the Observatory of Besancon, 20 jewels, brass-invar Guillaume balance adjusted by Quelos, blued steel balance spring with terminal curve.”
  • “Bulletin de Premiere classe de l'Observatoire National de Besancon awarded at the Timing Contest organised in 1913.”
  • “Mean average daily rate +/- 0,32 - Error of compensation at 20° +/- 0,136 - Mean error in 2 positions +/- 3,14”

Signatures and Documentation

The watch is consistently signed on the dial, case, and movement with the mark of L. Leroy & Cie. The serial numbers are recorded as 2769 for the movement and 9288 for the case.

The lot is accompanied by physical documentation in the form of copies of the original records from the 1913 timing contest and the award bulletin, providing context for the chronometric certification of this specific instrument.

Evidence for this section
  • “Signed on the dial, case and movement.”
  • “No. 2769, case No. 9288”
  • “In very good condition with copies of the timing contest records and of the Bulletin.”

Open research questions

  • What is the specific relationship between the adjustor Quelos and L. Leroy & Cie. regarding the balance adjustments of this period?
  • Are there extant original records at the Observatoire National de Besançon that provide further technical details on the specific performance of this movement beyond the provided copies?

Source evidence

Recorded claims and source quotations for L. Leroy & Cie. Keyless Pocket Chronometer
FieldSource-reported valueSource quotation
MakerL. Leroy & Cie.“L. Leroy & Cie., Horlogers de la Marine”
Material18K Gold“Fine 18K gold keyless pocket chronometer.”
Case StyleBassine“Three body, massive, "bassine", polished.”
Movement size19 ligne“M. 19"'”
ObservatoryObservatoire National de Besançon“Bulletin de Premiere classe de l'Observatoire National de Besancon awarded at the Timing Contest organised in 1913.”
Balance typeBrass-invar Guillaume balance“brass-invar Guillaume balance adjusted by Quelos”
Serial number2769 (movement), 9288 (case)“No. 2769, case No. 9288”
ConditionVery good“In very good condition with copies of the timing contest records and of the Bulletin.”

Visible details

  • Hinged gold cuvette present
  • White enamel dial with sunk subsidiary seconds
  • Gold spade-style hour and minute hands
  • Punch-mark in the form of a viper's head on the movement

Research qualifications

  • Timing data presented is derived from provided copies of records
  • Exact individual watchmaker or assembler credited as 'Quelos' is an attribution of balance adjustment only

Photograph identity and source facts were screened before import; rights clearance remains pending.

Consulted source

L. Leroy & Cie., Horlogers de la Marine, 7 Boulevard de la Madeleine, Paris, No. 2769, case No. 9288, circa 1913. Fine 18K gold keyless pocket chronometer. Bulletin de Premiere classe de l'Observatoire National de Besancon awarded at the Timing Contest organised in 1913.

Reviewed 2026-10-26 · Record 947802842f

Terms in this record

Glossary explanations for terms named in this object’s record.

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