Quick facts
- Caliber
- 4006(automatic)
- Jewels
- 17–27
- Beat rate
- 19,800 vph
- Hacking / hand-winding
- No / No
- Water resistance
- —Pending verification
- Crown
- 3 o’clock
- Production
- 1966–1978
- Modern equivalent
- —Pending verification
Variants
The 4006 went into many case styles. These are the ones our sources document best.
| Reference | Market | Day wheel | Status |
|---|---|---|---|
| 4006-7000 | — | — | Pending verification |
| 4006-7010 | — | — | Pending verification |
| 4006-7020 | — | — | Pending verification |
| 4006-6027 | — | — | Pending verification |
Serial decoder
Enter the six-character serial from the case back. We use 1966 to 1978 for the 4006.
Possible production date, not a guaranteed date or an authentication. Production date is not the purchase date.
Full decoder with caliber and case codePrice guide
Prices appear after our first sampling of sold listings in November 2026.
| Condition | Low | Median | High |
|---|---|---|---|
A · Collector | — | — | — |
B · Serviced original | — | — | — |
C · Running, unserviced | — | — | — |
D · Project or suspected franken | — | — | — |
Sampled —, n = —, eBay sold listings viewed manually.
Checks before you buy
Make the alarm ring before you buy. Then check that the parts belong together, because Bell-Matic parts swap easily between models.
Alarm The alarm winds with the crown, sounds near the set time, and the button at 2 o'clock stops it. Seiko allows about 5 minutes either way.
An alarm that won't sound, won't stop, or goes off far from the set time.
Sources: Seiko 4006A technical guide. Our own photo comes with our first shoot.
Setting ring and crystal The inner alarm ring turns freely with the crown.
A ring that's stuck, sometimes because the wrong crystal presses on it.
Sources: Adventures in Amateur Watch Fettling. Our own photo comes with our first shoot.
Day and date The button advances the date. The date changes near midnight and the day near 1 a.m., so a short gap between them is normal.
Day and date about 12 hours apart, a sign of a date finger fitted the wrong way round.
Sources: Seiko's 4006A technical guide; Adventures in Amateur Watch Fettling. Our own photo comes with our first shoot.
Movement fit The movement sits firmly in the case.
A movement that knocks about, usually from a rusted or missing casing spring.
Sources: Adventures in Amateur Watch Fettling. Our own photo comes with our first shoot.
Dial, hands and ring combination Parts that match the reference and the year.
Parts swapped from other Bell-Matics, or hands painted over.
Sources: Beyond the Dial; dealer disclosure. Our own photo comes with our first shoot.
Common faults and service
Most Bell-Matic problems are mechanical wear you can see or hear: a loose movement, a sticking button, a rubbing rotor.
The casing spring that holds the movement can rust, break or go missing, so the movement moves in the case (Adventures in Amateur Watch Fettling)
A pusher that won't spring back can mean dirt in the tube or gasket, or a dislodged date corrector spring (Adventures in Amateur Watch Fettling)
Wear in the rotor bearing lets the rotor rub the bridge (The Watch Site)
A movement loose in the case
A pusher that won't spring back
A rotor rubbing the bridge
Seiko USA no longer services the 4006 and asks owners not to send it (checked 2026-10-26). Independent watchmakers still work on them; check parts before committing.
On Seiko USA's list of calibers no longer available for service; they ask owners not to send them (checked 2026-10-26).
Where to look
If you buy through these links, we may earn a commission. You pay the same price either way. Affiliate disclosure
How the Bell-Matic alarm works
Two springs live in a Bell-Matic. The mainspring runs the watch and winds automatically from wrist motion. A second spring powers the alarm, and you wind that one by turning the crown, according to Seiko’s 4006A technical guide. When the alarm time arrives, a hammer is released and strikes a sounding spring until the alarm spring runs down.
How to set a Bell-Matic
- Wind the alarm: push the alarm button in first, then turn the crown in its normal, pushed-in position. With the button pulled out, the crown doesn’t wind the alarm spring.
- Set the alarm time: pull the crown out one step, turn it to move the inner alarm ring, then push the crown back in.
- Set the time: pull the crown out to the last step.
- Switch the alarm on or off: pull the button at 2 o’clock out to arm it; push it back in to stop or silence it.
- Set the date: press the button to advance the date.
- Set the day: Seiko’s guide has you move the hands back and forth between about 9:30 p.m. and 1 a.m.
Seiko allows the alarm to go off up to about 5 minutes either side of the set time, so a few minutes’ difference is normal. The same goes for the calendar: the date changes near midnight and the day near 1 a.m.
17, 21 and 27 jewels
All three exist. Plus9Time’s scan of Seiko’s parts list shows a 27-jewel version for Japan and a 17-jewel version for export, and Beyond the Dial records 21-jewel watches as well. None of the three is a sign of a swap on its own.
What usually goes wrong
- A loose movement. The casing spring that holds the movement can rust, break or go missing, and the movement knocks about in the case.
- A sticking button. A pusher that won’t spring back can mean dirt in the tube or gasket, or a dislodged date corrector spring.
- A rubbing rotor. Worn rotor bearings let the rotor rub the bridge; one restoration on The Watch Site replaced the bearing assembly.
- Day and date 12 hours apart. Adventures in Amateur Watch Fettling traced this to a date finger fitted the wrong way round during an earlier service.
Seiko USA no longer services the 4006 and asks owners not to send it. Independent watchmakers do, so check that parts are available before you commit.
Parts that swap between models
Bell-Matic dials, hands and alarm rings fit across several models, so a watch can be all Seiko parts and still not be original. Beyond the Dial warns about mismatched dials, and one dealer disclosed that a previous owner had painted a 4006-7010’s original hands white. If the crystal is new, ask whether it’s a reproduction: Renou sells a newly made acrylic crystal for several Bell-Matic cases and says plainly it isn’t new old stock.
Sources
- Seiko, Cal. 4006A technical guide: winding, alarm, setting, tolerances. Plus9Time, Bell-Matic 4006A Technical Guide and Parts List.
- Beyond the Dial, Collector Guide Seiko Bell-Matic: history, versions, mismatched parts.
- Adventures in Amateur Watch Fettling, Bell-Matic: the Seiko 4006-7021 and The Blue Bell: faults.
- The Watch Site, Restoration: 68 Seiko 4006-7020 Bell-Matic: rotor bearing.
- Seiko USA, Estimated Price For Movement Service: service status.
FAQ
What is a Seiko Bell-Matic?
A mechanical alarm watch Seiko launched in 1966 on the 4006 automatic movement. A hammer strikes a spring inside the case when the alarm goes off.
How do you set the alarm on a Seiko Bell-Matic?
With the button at 2 o'clock pushed in, turn the crown in its normal position to wind the alarm. Pull the crown out one step, turn it to set the alarm time on the inner ring, and push the crown back in. Pull the button out to switch the alarm on, and push it back in to stop it.
How much is a Seiko Bell-Matic worth?
It depends on the reference, the jewel count and the condition. Our sampled ranges appear on this page after our first sampling in November 2026.
Can Seiko still service a Bell-Matic?
Not in the US. The 4006 is on Seiko USA's list of calibers it no longer services. Independent watchmakers still work on them.