Your Grand Seiko watch is built to the very highest standards to ensure that it keeps time as accurately as possible. In this section, we define the Grand Seiko Standard, what it means and how your watch is tested against it.
The “Grand Seiko Standard” is our own accuracy standard. Your watch has been tested individually and has met this standard. All Grand Seiko calibers are tested in the same way and for the same period but there are two standards, one for Grand Seiko men’s watches and another for Caliber 9S27 which is used in Grand Seiko’s women’s watches. This is because the smaller size of Caliber 9S27 results in a different level of precision.
The Grand Seiko Standard defined
The movement in your Grand Seiko watch has been tested in our facilities for a period of 17 days, in six different positions and at three different temperatures. It has achieved or surpassed the standards of accuracy shown on page The Grand Seiko Standard defined, with the accuracy being defined as a gain or loss per day (the “mean daily rate”).
We specify “target values” for actual use and these are -1 second to +10 seconds per day for all calibers except 9S85 and 9S86 (-1 to + 8) and -5 to +10 for 9S27.
To judge the precision of your watch against these values, please measure the gain or loss over a week to ten days, and not just for one day, and in normal conditions.
If the mean daily rate is outside these levels, we recommend adjusting the watch. Adjustment will be chargeable even within the guarantee period if the watch has been subject to any of the conditions below.
The watch has been used in ways that are not in line with the recommendations in this booklet, such as allowing it to be magnetized.
It has been opened or tampered with by anyone other than a Grand Seiko repair center.
It has been damaged as a result of a natural disaster such as a flood, fire or earthquake.
Guaranteed conditions have been altered.
The Grand Seiko Special Standard
The Grand Seiko Special Standard is a precision standard even higher than the Grand Seiko Standard. Watches that meet this standard are designated by the word “SPECIAL” printed on the dial.
The Grand Seiko Standard defined
|
Item |
Unit |
Standard |
Cal. 9S27 |
Special Standard |
|---|---|---|---|---|
|
Mean daily rate in six positions |
Second(s)/day |
−3.0 〜 +5.0 |
−3.0 〜 +8.0 |
-2.0 〜 +4.0 |
|
Mean variation of daily rate |
Second(s)/day |
Less than 1.8 |
Less than 3.2 |
Less than 1.6 |
|
Maximum daily rate between two consecutive daily rates in the same position |
Second(s)/day |
Less than 4.0 |
Less than 6.0 |
Less than 3.0 |
|
Variation of rate between positions horizontal and vertical |
Second(s)/day |
-6.0 〜 +8.0 |
-8.0 〜 +10.0 |
-5.0 〜 +7.0 |
|
Maximum daily rate between mean daily rate and any individual rate |
Second(s)/day |
Less than 8.0 |
Less than 13.0 |
Less than 7.0 |
|
Variation of daily rate per 1 °C between 8 °C and 38 °C |
Second(s)/day/ °C |
-0.5 〜 +0.5 |
-0.6 〜 +0.6 |
-0.3 〜 +0.3 |
|
Variation of daily rate per 1 °C between 23 °C and 38 °C |
Second(s)/day/ °C |
-0.5 〜 +0.5 |
-0.6 〜 +0.6 |
-0.3 〜 +0.3 |
|
Rate-resumption |
Second(s)/day |
-5.0 〜 +5.0 |
-6.0 〜 +6.0 |
4.0 |
|
Number of positions in inspection |
6 positions |
|||
|
Condition of temperature in inspection |
8, 23, 38 °C |
|||
|
Length of tests |
17 days |
|||
Description of Grand Seiko Standard Terminology
|
Item |
Meaning |
|---|---|
|
Position in inspection |
Five orientations are specified by the International Standard ISO3159 so as to carry out various kinds of tests for time keeping. In addition thereto, in the GS inspection, 12 o’clock Up position in the state where a watch taken off the wrist is placed, is added, six orientations are specified. (Dial Up, Dial Down, 12 o’clock Up, 3 o’clock Up, 6 o’clock Up, and 9 o’clock Up) |
|
Mean daily rate in six positions |
Mean value of a total of 12 daily rates measured in six different positions, respectively, for two days. This is a target value indicating basic loss/gain per day of a watch, however, it is required to comprehensively judge the actual accuracy performance in consideration of other items. |
|
Mean variation of daily rate |
Mean value of a total of six variations of daily rates between the first day and second day when measured in six different positions for two days each. It indicates the degree which daily accuracy stabilizes in each position. |
|
Maximum daily rate between two consecutive daily rates in the same position |
Maximum value of a total of six variations of daily rates between the first day and second day when measured in six different positions for two days each. It indicates the degree which accuracy per day changes at maximum according to positions. |
|
Variation of rate between positions horizontal and vertical |
Indicates loss/gain in two positions at which a watch is most frequently used in daily life. It is a difference between mean daily rates for two days when a watch is placed in the Dial Up position and mean daily rates for two days when a watch is placed in the 6 o’clock Up position. |
|
Maximum daily rate between mean daily rate and any individual rate |
Maximum difference value between daily rates for 12 days in the test initial stage and mean daily rates. It indicates the degree at which the daily rate varies according to the manner for placing a watch. |
|
Variation of daily rate per 1 °C between 8 °C and 38 °C |
Variation in daily rates per 1 °C between 38 °C and 8 °C in the same position (Dial Up position). It indicates loss/gain in the temperature environment (taken-off state from the wrist) where a watch is used. |
|
Variation of daily rate per 1 °C between 23 °C and 38 °C |
Variation in daily rates per 1 °C between 38 °C and 23 °C in the same position (Dial Up position). It indicates loss/gain in the temperature environment (worn state of the wrist) where a watch is used. |
|
Rate-resumption |
Value obtained by subtracting mean daily rates of initial two days from daily rate of the last inspection day. It indicates the degree at which daily rate stabilizes after usage for a predetermined period. |