Seiko

WATCHTIME

"Spring Drive accordingly achieves a far more accurate rate than a mechanical escapement. Seiko calculates the average deviation at 0.5 second per day and at most, 15 seconds per month.

We measured a deviation of 0.1 second per day on the wrist. After half a month, our test watch had gained 2 seconds."

WATCH CRUNCH

"Having recently purchased a pre owned Grand Seiko GMT spring drive I was curious to the accuracy of this movement. It's stated to 1 second per day, although this is accurate and better than COSC I know Seiko tend to play it safe and are usually well within their stated accuracy, even the old 7s26 movement is published at -20 +40 but with most I've had and a quick regulation most of mine were within 10 seconds per day. Well after a month of testing and in various wind states, although I don't know if it makes a difference, I was really impressed. Yes after a month it worked out at +.30 seconds a day. Impressive to me"

A BLOG TO WATCH

Best single place for explanation of Spring Drive (besides my own pieces here).

A SPRING DRIVE IS (in 25 words or less) CONTEST

Speaking for myself, I've had about 10 Spring Drives in total over 20+ years. I've been to the Epson facility where the Spring Drives are assembled.

I don't keep record of specs because I have so many other mechanical watches to take care of and the SDs just keep on tickin' (whoops, I mean gliding)

The first generation sold in Japan 1999-2000, manual wind, 500 copies. I got this in 2005

SPGA001 first public generation sold widely. I got this in 2005

Early Credor moonphase. I got this in 2006

First Release "Snowflake" perhaps the most widely-known Spring Drive. I bought this in 2007.

The Ghastly Seiko Galante, for overly style conscious Japanese (IMHO). I don't know why I bought it in 2008 -- I suppose to "have one of everything"

Early Credor version of the first gen Spring Drive, my Japanese friend had it from early 2000's I got it 2012