Seiko · Seiko 4R37

Seiko 5 Sports Helmet, SSA297 and Superior power reserve: inside the 4R37

The Seiko 5 Sports Helmet and Diastar, the SSA295 and SSA297, and the Seiko Superior SSA051 all run on the 4R37, a 4R35 with a 24-hour subdial. From a full wind it runs about 41 hours, or 1.7 days.

Updated September 2026 · Based on manufacturer specs, published reviews and watchmaker/owner reports

Watches that use the Seiko 4R37

The 4R37 is the member of Seiko's 4R family with a small 24-hour subdial at about 10 o'clock. It appeared mostly in Seiko 5 Sports and Seiko Superior models from the mid-2010s, which are often easier to find secondhand now than new. If your Seiko has a date at 3 and a little 24-hour dial on the left, this is probably the movement inside.

Don't confuse it with the 4R34 in the Seiko 5 Sports GMT. The 4R34's 24-hour hand can be set to a second time zone. The 4R37's can't.

Specs at a glance

History and where it came from

Seiko launched the 4R family around 2011 to replace the 7S26 and 7S36 in its affordable automatics, adding the hacking and hand-winding that the older calibres lacked. The 4R37 is a variant of that platform. Seiko's technical guide describes the 4R37A as based on the 4R35B, with "a small 24-hour clock in the 10 o'clock direction".

It found a home in the Seiko 5 Sports range of the mid-2010s. The "Helmet" models (SSA281 to SSA284) revived the tall, sloping case of the 1970s 6318-7100, and the "Diastar" versions (SSA285 to SSA289) put the same design on straps. Worn & Wound reviewed the SSA285 in early 2017. Around the same time, Seiko used the 4R37 in its Superior compass watches, including the SSA051 and the limited-edition SSA059. Outside Seiko, SII offers the design as the NH37.

Accuracy in the real world

Seiko rates the 4R37 like the rest of the 4R family: +45 to -35 seconds a day, worn on the wrist between 5°C and 35°C. The technical guide adds bench tolerances: within 20 seconds a day dial up when fully wound, and within 30 seconds in the other test positions and after 24 hours of running.

Real examples often do much better. Worn & Wound's Seiko Superior SSA059 ran at +3.9 seconds a day during its review. Owners of 4R-family watches commonly report somewhere between a few and 20 seconds a day fast. Like all 3 Hz movements that aren't adjusted in multiple positions at the factory, the rate varies with how the watch sits overnight and how fully it's wound.

It regulates easily. A watchmaker can bring a healthy 4R37 closer to zero quickly and cheaply.

Reliability and servicing

Mechanically, the 4R37 is a 4R35 with an extra wheel to drive the 24-hour hand. It shares Seiko's Diashock protection and Magic Lever winding with the rest of the family, which has a long record of shrugging off daily wear.

Servicing is where it differs slightly from the 4R35 and 4R36. Those are so common that many watchmakers simply swap in a new movement. A 4R37 or NH37 is less common, so check that a replacement is available before assuming a swap. A normal clean and oil is straightforward for any watchmaker who works on Seiko movements, and Seiko's own service centres handle it too.

Quirks worth knowing

• The 24-hour hand isn't a GMT. It moves with the hour hand and can't be set on its own. Its job is to show AM or PM. Worn & Wound's Diastar reviewer didn't find it especially useful.
• It does make date-setting easier. Seiko's manual says to check AM or PM on the 24-hour hand while setting the time, so the date changes at midnight rather than noon.
• A shorter danger zone. Seiko's manual says not to set the date between 9pm and 1am. Here's why.
• Crown positions. Normal position winds (clockwise only), the first click sets the date counterclockwise, and the second click sets the time and stops the seconds hand.
• A rough sun compass. On the Superior models, Worn & Wound describes lining up the 24-hour hand with the sun to find north using the inner compass ring.
• Two crowns on the Superior. The second crown turns the inner compass ring, not the movement. Don't confuse the two when winding.

How it compares

• Seiko 4R35 / 4R36: the same movement without the 24-hour hand, in the Seiko 5 Sports SRPD, Turtle and Cocktail Time. Same reserve and accuracy.
• Seiko NH34 / 4R34: the one to choose if you want a real second time zone. Its 24-hour hand is set independently.
• Seiko 4R39: another 4R with a 24-hour hand, used in Presage models such as the Style60's 24-hour.
• Seiko 7S26: the older Seiko 5 movement. Tough, but no hacking or hand-winding.
• Seiko 6R35: Seiko's step up, with a 70-hour reserve and a tighter spec.

Living with the 41-hour reserve

Take your Seiko 5 Helmet off on Friday evening and it will usually have stopped by sometime on Sunday. A Superior SSA051 that only comes out for hikes will need winding before every outing. On a stopped 4R37, you'll set the time with the 24-hour hand on the right side of noon, then set the date, keeping clear of the 9pm-to-1am window.

It also charges slowly on quiet desk days, so the real figure is often shorter than 41 hours. Watch Winder counts down the reserve for each watch you own and reminds you before it stops, so you can wear it or give it a few dozen turns of the crown in time. For a one-off check, try the "Will my watch stop?" calculator.

Verdict

The 4R37 is a dependable 4R35 with a bit of extra dial interest. You get hacking, hand-winding, the family's toughness and a 24-hour subdial that helps you set the date correctly, even if it's not much use otherwise. If you want a proper second time zone, look at the 4R34 instead. If you like the Helmet or Superior designs, the movement won't hold them back, apart from the short 41-hour reserve.

FAQ

How long does a Seiko 5 Sports Helmet run off the wrist?

About 41 hours from a full wind. Taken off on Friday evening, a Seiko 5 Helmet will usually stop some time on Sunday.

Is the 24-hour hand on the Seiko SSA297 a GMT?

No. The 4R37's 24-hour hand is linked to the hour hand and only shows whether it's AM or PM. For a settable second time zone you need a 4R34, as in the Seiko 5 Sports GMT.

Does the Seiko Superior SSA051 hack and hand-wind?

Yes. Its 4R37 stops the seconds hand when you pull the crown to the second click and winds when you turn the crown clockwise in the normal position.

How accurate is the Seiko 4R37?

Seiko rates it at +45 to -35 seconds a day on the wrist. Many run much better; Worn & Wound's Superior SSA059 ran at about +3.9 seconds a day.

What's the difference between the 4R37 and the 4R35?

The 4R37 is based on the 4R35B and adds a 24-hour subdial at about 10 o'clock. It also has 24 jewels to the 4R35's 23. Reserve and accuracy are the same.

When should I not set the date on a Seiko 4R37?

Seiko's manual says to avoid setting the date between 9pm and 1am, when the date-change mechanism is engaged.

Sources

• Seiko: Cal. 4R37A parts list and technical guide
• Seiko: Cal. 4R35/4R36/4R37 instruction manual
• Worn & Wound: Seiko Superior SSA059 review
• Worn & Wound: Hands-on with the Seiko 5 Sports "Diastar" SSA285K1
• My Eastern Watch Collection: Seiko 5 Sports "Helmet" SSA283K1 review

Keeping it running

• On an average day an automatic gains roughly 4 hours of reserve per hour on the wrist, so about 10 hours of wear fills the Seiko 4R37. Desk days charge more slowly.
• Most automatics can also be wound by the crown. If yours has stopped, a few dozen turns gets it going before you put it on.
• Off the wrist it stops about 41 hours after it was last full. Stopped sooner?
• On a watch winder, start at about 650 turns per day, both directions. Winder settings for every movement.
• If it does stop, don't set the date between 9pm and 3am. Check if it's safe.

All Seiko movements

Never let it stop

Watch Winder counts down the reserve of every watch you own and reminds you before one stops. It already knows the Seiko 4R37: type your watch's name and the reserve fills itself in.

Manufacturer's published figure. Real reserve varies with the watch's age and service; check your manual.