I bought the black and blue versions of this fine watch. They serve as my day-to-day watch. As noted in other reviews, a self-winding watch is more accurate than a mechanical watch but far less accurate than a quartz watch. Quartz watches are off by about 2-3 seconds/month, compared to atomic clocks. Self-winding watches are off by about 7 minutes/month. I've found the difference to be negative not positive. Sieko says about 5 minutes/month.

But, here's one advantage: you won't have to wind it, just wear it. That makes it the best watch available in the future ahead. It's getting harder to get my battery replaced on quartz watches and it will likely become impossible in future.

It only takes about 39 hours for the battery to run down so it helps to rotate it (to wind) about 2-3 minutes a day. I can usually wind it in a commercial break.

The drawbacks with the black model:

* harder to keep clean;

* the day and date diasl are harder to read because the face is black and so are the letters.

All in all, it's a great watch.

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My review of the blue watch:

Xbar 107 seconds/week (runs fast) (7 min./month compared to 2-4 sec./month quart watch)
St DEV 27 sec.
N = 7
95% CI 2.447 using Student's t
m+ = 136 seconds/week
m- = 78 seconds/week

Summary:

Good points:
* Beautiful with dark blue face, white symbols, functional medium blue nylon band;
* Easy to read, even in the dark;
* Easy to use with uncomplicated settings similar to other watches;
* Compact design;
* Measurement consistency is excellent compared to quartz mechanism.

Bad points:
* Difficult to set time (see instruction below);
* Gains 10 seconds a day (consistency); and
* Does not have a manual wind stem.

Discussion
This watch looks great. Unlike other self-winding or kinetic watches, this one is compact. In the best tradition of Japanese product development they thought hard on how this watch should function and say about the wearer. The hands are easy to reading, even for those of use with failing eyesight. The second sweep hand has a red tip allowing easy setting of the time.

Unlike some Japanese product, they provided a short, simple instruction on winding the watch. Here, I am comparing them to Citizen's ecco-drive watch, which I also own. Just gently work your arm back and forth for three minutes and the self-wind watch will charge; or, you could wear it for a day.

Okay, now for the negatives. First, this is not your quartz watch. The original self-winding mechanism was invented, according to Wikipedia, by a Swiss watchmaker in 1770. Since then it has gone through several improvements but is not as accurate as the quartz mechanism popularized starting in the 1970's. Sieko warns that this watch could be off by as much as 10 seconds a day. One days use indicates that my watch runs about 10 seconds fast.

The great watchmaker Harrison, who invented the first chronometer accurate enough to track longitude, said that consistency is more important than accuracy. (A poor copy of one of Harrison's chronometers was carried by Captain Cook on his circumnavigation of the globe. He had nothing but good things to say about it.) I have another self-winding watch, an Armitron, which runs consistently 15 seconds fast on days that I wear it.

From my measurements of quartz watches, their accuracy, while dazzling when compared to old hand-wound watches, are less accurate than my old German pendulum clock. So I am told, the longer the arm, the more stable the swing and the more accurate the timepiece. I compare everything to atomic time. And, because the quartz mechanism is battery-driven, it seems to suffer from inconsistency. I carefully measured my collection of six quartz watches over a 2 year period. While the battery was new, the error was consistent. As the battery burned out, the error became difficult to predict. Sometimes a positive error (adding time) would become a negative error (losing time) as the battery died. This dying period was also hard to predict.

The accuracy of the quartz mechanism is not as good as my pendulum clock. They all lost or gained approximately 2-3 seconds, on average, per month.

Based on a week of measurements with the Armitron, I would say that it is shockingly inaccurate but consistently so. Assuming that the Sieko error continues to be consistently 10 seconds fast this will mean that I will have to reset it every week. This is a small price to pay for an otherwise beautifully crafted and honestly-priced handiwork.

Setting time
The date and day are fairly easy. I suggest turning the watch arms until the click past a day so you won't be twelve hours off.

Setting the time is another matter. What works best is to set the hour and minute hands, then gently hold the second hand. It should pulse a little as it tries to force itself forward. Once the seconds are accurate, release and the second hand should be accurate. It takes a little practice at first and don't set the time until you pump the watch 3 minutes to charge the spring.

Time to unwind
It takes about 39 hours (1 test) to unwind.