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The Encyclopedia of Horology

Calibre database

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Specifications

FieldFrench round (Paris) clock movement
Makerjapy-freres
CountryFrance
Periodc. 1840 to the early twentieth century
DiameterTypically around 80 to 100 mm across the round plates
HeightShallow drum-shaped assembly
JewelsGenerally unjewelled; some better movements jewelled at the escapement
FrequencyPendulum-regulated; rate depends on pendulum length rather than a vibration figure
Power reserveEight-day run between windings on most examples
WindingKey wind through the dial or back
SettingHands set by key or by hand at the dial
EscapementBrocot or plain deadbeat; recoil on cheaper work
BalancePendulum, frequently with a Brocot suspension for rate adjustment from the dial
ComplicationsHour and half-hour striking on a bell or gong, Rack or count-wheel striking depending on date
ArchitectureTwo circular brass plates carrying the going and striking trains in a compact drum, made as a standardised unit by specialist movement factories in Paris and the Franche-Comté and sold to case makers across Europe.