Seiko 6159A

Probable

The caliber of the first Tuna. Running at 36,000 vph — 10 Hz — it is among the fastest mechanical movements Seiko has produced, and the beat rate is itself a diagnostic: the seconds hand advances in ten steps per second, visibly smoother than the six of a 21,600 vph caliber.

Specifications

Movement manufacturer: Seiko
Production: 1975–1978
Frequency: 36,000 vph (5 Hz)
Winding: automatic
Complications: Day-date · Hacking seconds

Architecture

High-beat automatic day-date caliber with hacking, developed for the professional dive watch.

Service practice

A high-beat caliber wears its escapement faster and demands correspondingly better lubrication and more frequent service. Parts are not manufactured. This is the Seiko caliber where a documented service history most affects what the watch is worth.

References using this caliber

Seiko 6159-7010Factory
Prospex · 1975–1978

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

Monochrome Watches — the history of the Seiko Tuna

Monochrome Watches

Accessed: 2026-08-18

Cited for

This referenceProbable

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Last verified: Not yet reviewed