Seiko 6105B
ProbableThe caliber of the 6105-8110 'Willard'. The 6105A preceded it in the earlier -8000 case; both are 6105-family movements and therefore both satisfy the case number, so distinguishing them requires reading the movement itself.
Specifications
- Movement manufacturer
- Seiko
- Production
- 1970–1977
- Frequency
- 21,600 vph (3 Hz)
- Winding
- automatic
- Complications
- Date
Architecture
Automatic diver's caliber with a date, developed from the 6106 family.
Service practice
Parts are no longer manufactured. Movements assembled from several donors are common and are legitimate repair work — but they mean the movement cannot be used to date the watch.
Open questions
Seiko 6105A and 6105B: what actually differs
What is the substantive difference between the 6105A and 6105B executions — hacking, date quickset, or a purely constructional revision — and exactly when did production change over?
Best current answer
The 6105A is associated with the symmetric-cased 6105-8000 and the 6105B with the asymmetric -8110. The catalog records that association and does not assert what the letters denote functionally.
Conflicting claims
Collector sources describe the difference variously as a hacking capability, a date-setting change and a bridge revision, without agreement and without citing a Seiko technical guide. A Seiko technical guide for the 6105 family would settle it.
Scope Affects the movement fitments on 6105-8000 and 6105-8110 and any authentication note that turns on which execution belongs in which case.
Related calibers
Succeeded by
Seiko 6105AFitted to the later asymmetric-cased 6105-8110 and -8119.
References using this caliber
- Seiko 6105-8110Factory
Prospex · 1970–1977
Provenance of this record
Sources & Evidence
Seiko caliber technical guides and parts catalogues
Seiko Watch Corporation / Seiko Instruments
- Accessed
- 2026-08-18
Cited for
The Seiko Guy — model and reference guides
The Seiko Guy
- Accessed
- 2026-08-18
Cited for
Last verified: Not yet reviewed