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Seiko 7S26

High confidence

The caliber of the SKX and of an enormous number of Seiko 5 watches. It does not hack and it does not hand-wind, and it has no regulator arm accessible for fine adjustment in the conventional way — it was designed to be replaced rather than serviced.

Specifications

Movement manufacturer
Seiko
Production
1996–2019
Frequency
21,600 vph (3 Hz)
Jewels
21
Power reserve
41 hours
Winding
automatic
Complications
Day-date

Architecture

Automatic day-date caliber with a magic-lever winding system, designed for low cost and long service intervals rather than for adjustment.

Authentication notes

  • MovementHigh confidence

    Hacking or hand-winding rules out a 7S26

    If the seconds hand stops when the crown is pulled, or the crown winds the mainspring, the movement is not a 7S26 — most likely a 4R36, which is dimensionally compatible and is a common upgrade. On a watch presented as an original SKX007 that is a modification finding, and it is the check that also catches complete counterfeits, which rarely bother to reproduce the absence of a feature.

Related calibers

  • Succeeded by

    Seiko 4R36

    The 4R36 adds hacking and hand-winding and fits the same cases.

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
Primary sourceManufacturer documentation

Seiko — Prospex, Presage, 5 Sports and Astron product documentation

Seiko Watch Corporation

Accessed
2026-08-18

Cited for

This referenceHigh confidence
View source ↗

Last verified: Not yet reviewed