Need a part for this caliber? Supporters unlock the parts catalog, factory equivalents, and the donor finder that shows which other movements can supply the part you need.
Become a Supporter
Seiko 6138B
Automatic · 12‴ · Japan · 1972
Dimensions
27.4 mm
Height
8.00mm
Jewels
23
Power reserve
45h
Timegrapher
Beat rate
21,600bph
Frequency
3Hz
Reference: healthy amplitude ≈ 270–315° fully wound (>200° at 24 h); beat error ideally < 0.5 ms.
Movement
| Movement type |
Automatic
Mechanical movements fitted with an oscillating rotor that winds the mainspring through the wearer's natural motion. Invented by Abraham-Louis Perrelet around 1777 for pocket watches and adapted to the wristwatch by John Harwood in 1923, it combines traditional craftsmanship with everyday convenience.
|
|---|---|
| Winding type |
Automatic (Rotor-Driven)
Self-winding via a rotor whose motion winds the mainspring through a transmission gear train. The specific rotor configuration (central, micro, peripheral, bumper) is catalogued separately under Rotor Type. Standard on the vast majority of mechanical wristwatches since the mid-20th century.
|
| Setting type |
Stem Set (Crown Pull)
The dominant modern system: pulling the crown out to a setting position engages the hand-setting mechanism. Introduced in the late 19th century and refined into multi-position crowns (date, time, GMT). Used in virtually all modern wristwatches and most 20th-century pocket watches.
|
| Escapement type |
Swiss Lever
The undisputed standard of modern mechanical watchmaking. Through an elegant interplay between escape wheel, pallet fork, and balance, it delivers reliable impulses with the safety of 'draw' to keep the lever locked. Refined since the 18th century, it powers almost every quality mechanical wristwatch made today.
|
| Control type |
Balance Wheel
The heart of mechanical timepieces, the balance wheel is an oscillating component that, together with the hairspring, forms a harmonic oscillator regulating the gear train's pace. Its steady back-and-forth motion ensures the even release of energy from the mainspring, governing the watch's accuracy.
|
| Regulator type |
Pinned Regulator (or Index Regulator)
The most traditional regulator, consisting of a movable index pointer fitted with two curb pins (or a pin and a boot) that embrace the hairspring. Sliding the index along its scale changes the spring's active length, adjusting the rate. Simple, reliable, and easy to service, it remains the workhorse standard across countless mechanical movements.
|
| Rotor type |
Central Rotor
The most common automatic winding rotor, mounted on the central axis of the movement and rotating a full 360°. Industrialized by Rolex with the Perpetual system in 1931 and refined throughout the 20th century, it offers excellent winding efficiency and remains the de facto standard for automatic wristwatches, whether winding in one or both directions.
|
| Shock protection |
Diashock
Seiko's in-house shock protection system, introduced in 1956 and refined ever since. Functionally similar to Incabloc but with proprietary geometry tailored to Seiko calibres, from entry-level 7Sxx automatics to high-end Grand Seiko movements. A cornerstone of Seiko's reputation for mechanical durability.
|
Specifications
| Lignes | 12‴ |
|---|---|
| Shape |
Round
It is the most common form that we can find.
|
| Complications |
Day
Beyond hours and minutes, the day complication anchors wearers to their weekly schedule, providing context to our cyclical routine.
,
Date
An essential for many, the date display reminds wearers of their daily commitments, connecting the abstract concept of time to tangible daily events.
,
Chronograph Second
The heart of the chronograph function, the chronograph second hand provides real-time tracking of elapsed seconds when the chronograph is activated. Usually centrally mounted, its smooth or ticking movement around the dial offers a visual spectacle and allows wearers to measure events with precision up to a second.
,
Chronograph Minute
A fundamental component of the chronograph mechanism, the chronograph minute sub-dial records elapsed minutes once the chronograph is engaged. Typically counting up to 30 or 60 minutes, this feature extends the utility of the chronograph function beyond just seconds, making it invaluable for capturing extended events.
,
Chronograph Hour
Deepening the chronograph's utility, the chronograph hour sub-dial keeps track of elapsed hours when the chronograph function is running. Often located in a dedicated sub-dial, this complication allows for the measurement of longer durations, expanding the watch's timekeeping versatility.
|
| Hand count | 4 |
| Hand sizes | 1.50 x 0.90 x 0.26 / 0.26 x 0.26mm |
| Further measures | Mounting Diameter (Dm): 27.0mm Dial Spacer: 0.2mm |
Origin & References
| Manufacturer | Seiko |
|---|---|
| Country | Japan |
| Launch year | 1972 |
| COSC certified | Yes |
| Signature | 1974: Seiko, Japan, 21 Jewels; Diashock |
Notes
Remarks: 1972-1979
sophisticated excenter self-winding mechanism with just one gear stage (Fig.4)
like 6138A, only minor modifications of switching mechanism (dial side)
An old archive entry contains a sample with 17 jewels (after signature), but it is not sure whether the rotor bridge of this sample was swapped.
Other data: balance staff: Seiko 315611 stem: Seiko 354616 mainspring / battery: Seiko 401616
Ranfft mentioned about this caliber: There are variants with this quantity of jewels 21, 23
sophisticated excenter self-winding mechanism with just one gear stage (Fig.4)
like 6138A, only minor modifications of switching mechanism (dial side)
An old archive entry contains a sample with 17 jewels (after signature), but it is not sure whether the rotor bridge of this sample was swapped.
Other data: balance staff: Seiko 315611 stem: Seiko 354616 mainspring / battery: Seiko 401616
Ranfft mentioned about this caliber: There are variants with this quantity of jewels 21, 23
Family
Series 6100A - 6186A
* ) quickset, turning crown (else pushing)
**) day in 2 languages
manual wind, 21600 A/h:
6100A: -
6102A: date
6110A: like 6100A, Railroad Watch
automatic, 21600 A/h:
6105A: date*
6105B: date*, hack feature
6106A: day, date, hack feature, 2 rotor screws
6106B: day, date, hack feature
6106C: day**, date, hack feature
6109A: day, date, smaller rotor
6117A: date*, GMT 24h
6117B: date*, GMT 24h, hack feature
6118A: date*
6119A: day, date, 2 rotor screws
6119B: day, date
6119C: day**, date
chronograph, 21600 A/h:
6138A: hour counter, day*/**, date*
6138B: same, modified switching mechanism
6139A: day**, date
6139B: same, modified switching mechanism
automatic, 36000 A/h:
6145A: date, Grand Seiko
6146A: day, date, Grand Seiko
6155A: date, GS Special
6156A: day, date, GS Special
6159A: date*, Diver 300
6159B: date*, hack feature, Diver 600
6185A: GS Veri Fine Adjusted
6185B: dito, hack feature
6186A: day, date, Unruhstop, GS Veri Fine Adjusted
**) day in 2 languages
manual wind, 21600 A/h:
6100A: -
6102A: date
6110A: like 6100A, Railroad Watch
automatic, 21600 A/h:
6105A: date*
6105B: date*, hack feature
6106A: day, date, hack feature, 2 rotor screws
6106B: day, date, hack feature
6106C: day**, date, hack feature
6109A: day, date, smaller rotor
6117A: date*, GMT 24h
6117B: date*, GMT 24h, hack feature
6118A: date*
6119A: day, date, 2 rotor screws
6119B: day, date
6119C: day**, date
chronograph, 21600 A/h:
6138A: hour counter, day*/**, date*
6138B: same, modified switching mechanism
6139A: day**, date
6139B: same, modified switching mechanism
automatic, 36000 A/h:
6145A: date, Grand Seiko
6146A: day, date, Grand Seiko
6155A: date, GS Special
6156A: day, date, GS Special
6159A: date*, Diver 300
6159B: date*, hack feature, Diver 600
6185A: GS Veri Fine Adjusted
6185B: dito, hack feature
6186A: day, date, Unruhstop, GS Veri Fine Adjusted
Related calibers
Seiko 6105A
Seiko 6105B
Seiko 6106A
Seiko 6106B
Seiko 6106C
Seiko 6117A
Seiko 6117B
Seiko 6118A
Seiko 6119A
Seiko 6119B
Seiko 6119C
Seiko 6138A
Seiko 6138B
Seiko 6139A
Seiko 6139B
Compatible Parts
829 other catalog sources can supply compatible parts for this caliber.
108 compatible parts catalogued · find a donor to harvest a scarce part.
Supporter feature — sign in as a supporter to browse the parts and donor sourcing.