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Movement · Seiko · automatic

Seiko 4R38 movement

Seiko 4R38 is an automatic movement by Seiko: beating at 21,600 bph1, 41 h1 of power reserve. 1 watch in our base uses it: SSA405 (list).

Sources checked · How we source numbers

4R38 at a glance

Beat rate
21,600 bph1
Power reserve
41 h1
Accuracy
−35 to +45 s/day1
Do not set the date
21:00–01:001

New to the terms? Read quartz vs automatic or watch movement types.

Setting and servicing the 4R38

The figures a watchmaker or a timegrapher needs for the 4R38, as Seiko prints them.

Accuracy (maker)
−35 to +45 s/day1only if worn on the wrist 5 C to 35 C
Power reserve
41 h1
Do not set the date
21:00–01:001
Hacking seconds
Yes1
Hand winding
Yes1

Same family at Seiko

How each differs from the 4R38, worked out from the figures on its own page.

Watches with the 4R38

All 4R38 figures

Every figure we hold for the 4R38, with its source. Where sources disagree, each value is shown.

Running

Beat rate
21,600 bph1
Power reserve
41 h1
Hacking seconds
Yes1
Hand winding
Yes1

Accuracy and care

Accuracy (maker)
−35 to +45 s/day1
Do not set the date
21:00–01:001

Not published yet

  • Hands and functions: not published by Seiko
  • Diameter: not in the documents we read
  • Height: not in the documents we read
  • Jewels: not published by Seiko
  • Lift angle: not in the documents we read
  • Hand holes: only in Seiko’s drawing; not read yet
  • Dial feet: not published
  • Stem part number: not published by Seiko

4R38 questions

How accurate is the 4R38?

Seiko rates the 4R38 at −35 to +45 s/day, measured under Seiko’s own test conditions; a worn 4R38 can run outside the −35 to +45 s/day range.

Source [1]

How long does the 4R38 run when fully wound?

About 41 h from a full wind, per Seiko.

Source [1]

When should you not change the date on the 4R38?

Not between 21:00 and 01:00, per Seiko: the 4R38’s date change is engaged then, so move its hands past 01:00 before using the quick-set.

Source [1]

Does the 4R38 hack and hand-wind?

Yes, it hacks: the seconds hand stops with the crown pulled out. It can be wound by the crown.

Source [1]

Which watches use the 4R38?

1 watch in our base name the 4R38: SSA405.

More on movements

Sources

Documents checked · Report a wrong number

  1. 1Seiko Watch Corporation — Mechanical watch instructions, Cal. 4R35/4R36/4R37/4R38/4R71/4R72/4R39 (EN) · pdf · read
  2. 2Seiko Watch Corporation — SSA405J1 product page (Presage), seikowatches.com global-en · html · read