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Seiko

Seiko Epson goes by JIS standard no. B7025 for rating accuracy, which requires a few years of crystal aging date that didn't exist when the 9RA movements were launched

 

Seiko Epson released a technical paper on the 9RA movements years ago, they knew the 9RA movements could perform to +/-10 seconds a year when new.





You can access a PDF of the paper from this site, but it is in japanse.
www.jstage.jst.go.jp

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