Seiko Caliber 4006A
Seiko Caliber 4006A

Seiko Caliber 4006A

ManufacturerSeiko Time Corp.
Caliber Number4006, 4006A
In-House?
Yes
Movement TypeAutomatic, self-winding mechanical
Diameter
31.2mm
Height
7.15mm
Jewel Count
17 / 21 / 27
Beat Rate
19,800 bph
Lift Angle
52 or 58 degrees (unconfirmed)
Rotor Winding Direction
Bi-directional (Magic Lever)
Manual-Winding?
No
Mainspring Count
2
Anti-Shock Device
Diashock
Hand Count3
FunctionsCentral hours; central minutes; central sweeping seconds; day and date at 3:00; alarm
Hacking Seconds?
No
Country of ManufactureMade in Japan
Known Models
Seiko Bell-Matic, Seiko Business Bell (Add your watch to the comments below…)

The Seiko caliber 4006A is a vintage automatic movement watch a built-in mechanical 10 second alarm mechanism. This calibre is found in Seiko Bell-Matic watches which were produced in the 1960s into 1970s.

Seiko cal. 4006A can be found with 17, 21, or 27 jewels depending on what market the watch was intended for.

How to set the alarm:

The Bell-Matic has an internal rotating bezel with a red arrow pointing to the time you set the alarm for.

There is a button at 2:00 that has 3 positions. When pressed in, the button serves to quickset the date (off topic, but the day of the week is not quickset).

The alarm functions via a spring that gets wound up when you have the button in neutral position and wind the crown. Winding the crown does not wind the movement.

The button also pulls out one click to engage alarm mode. When the alarm is activated or buzzing, press the button back to neutral position to turn it off.

Similar Calibers:

There is a Seiko caliber 4005A which is the date-only version of the 4006A.

Video – Seiko Bell-Matic 4006-6010 Alarm Sound:

Video – Bellmatic Disassembly and Assembly:

Additional Resources:

Seagull Caliber St19

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