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The Encyclopedia of Horology

Calibre database

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Specifications

FieldSeiko calibre 7A28
MakerSeiko
CountryJapan
PeriodFrom 1983
DiameterNot recorded in a source consulted here
HeightNot recorded in a source consulted here
Jewels15 jewels
FrequencyQuartz, with independent stepping motors for the chronograph hands
Power reserveBattery powered
WindingNot applicable; battery powered
SettingCrown setting
EscapementNone; quartz oscillator with stepping motors
BalanceNone; quartz oscillator
ComplicationsAnalogue chronograph reading to one-tenth of a second, Independent chronograph hands driven by separate motors
ArchitectureThe first analogue quartz chronograph movement, using three separate stepping motors so that the chronograph hands run independently of the timekeeping train and can be reset instantly.