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Seiko 6309A

Probable

One of the most numerous mechanical watch movements ever made. Neither hacks nor hand-winds; both absences are correct. Its ubiquity is why 6309 parts are still available and why 6309-cased watches carry so much service history.

Specifications

Movement manufacturer
Seiko
Production
1976–1988
Frequency
21,600 vph (3 Hz)
Jewels
17
Winding
automatic
Complications
Day-date

Architecture

Automatic day-date caliber, non-hacking and without hand-winding, produced in very large numbers for export markets.

Service practice

Service parts, including complete replacement movements, circulated widely. A 6309 running a later-production movement is ordinary and is an originality note, not a finding.

Related calibers

  • Related caliber

    Seiko 6306A

    Export equivalent, without hacking and with four fewer jewels.

References using this caliber

Provenance of this record

Sources & Evidence

Primary sourceTechnical documentation

Seiko caliber technical guides and parts catalogues

Seiko Watch Corporation / Seiko Instruments

Accessed
2026-08-18

Cited for

This referenceHigh confidence
Secondary sourceSpecialist publication

Worn & Wound — Seiko diver and Daini Seikosha deep dives

Worn & Wound

Accessed
2026-08-18

Cited for

This referenceProbable
View source ↗

Last verified: Not yet reviewed