Seiko Caliber Nh05a Movement

Seiko (SII) Caliber NH05A

Seiko Caliber Nh05a Drawing

ManufacturerSeiko
Caliber NumberNH05A (aka NH05)
Movement TypeAutomatic
Jewels21
Diameter7 3/4”’ (17.5mm)
Height5.92mm
Vibrations Per Hour
21,600 bph
Shock SystemDiashock
Power Reserve
50 hours
Winding Direction
Bi-directional
Hands100/65/21
Stem351-420
Lift Angle52 degrees
Hacking?Yes
Hand-Windable?Yes
FunctionsHours, minutes, central seconds, date calendar
Country of ManufactureJapan/Malaysia
Known Brands
EC Andersson North Sea II (add more in the comments below)

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The Seiko/TMI/SII/Epson caliber NH05 is a hand-windable and hacking automatic movement. At only 17.5mm diameter it is a fairly small movement and ideal for ladies size watches.The mainspring of this caliber is fully wound after 55 turns of the crown.

Accuracy

Time Module documentation claims an accuracy rating of -35 ~ +55 seconds per day. E.C. Anderson is a brand know to use this movement in their North Sea II watch, and they regulate the movements by hand in-house before shipping.

At the time of this post, caliber NH05 replacement prices were found online for $69.29.

The only watch brand we currently know is using this movement is E.C. Andersson in the North Sea II. This is what is posted on their site about it:

E.C.Andersson uses the SEIKO NH05, a movement that is beloved around the world. Known to be extremely reliable, thanks to the solid built. The SEIKO NH05 often outlives many of its competitors by far, and are easy to service.

Seiko Caliber Nh05a Movement

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Don
Don
2 years ago

Do small movements like this have as good of accuracy as larger ones?

Jorge E Robles
Jorge E Robles
2 years ago
Reply to  Don

Yes, they can be capable of good to excelent accuracy and precision as larger ones. The problem is how much are you willing to pay for such level? Best example is the Rolex 2135 for Ladies watches. It is not only precise, it is able to pass chronometer grade tasting with ease, and it has been a workhorse in the Rolex line up for years, may be decades, and require just basic servicing. But those… Read more »

Heiner Klaus
Heiner Klaus
2 years ago

Askania, a brand from Berlin, uses this movement as well, eg. in their square C. Bamberg

Buck
Buck
1 year ago

This is the upgraded SII version of the Seiko 4205, with a larger winding weight (for improved winding efficiency) and the full 21jewels.

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